A method of growth simulation of a silica aerogel structure

Abstract

This invention discloses a method for simulating the growth of silica aerogel structures. The method includes the following steps: S1, establishing a molecular model of orthosilicic acid molecules and performing energy minimization calculations; S2, establishing an amorphous box; S3, performing energy minimization and molecular dynamics relaxation calculations on the amorphous box; S4, performing simulation condensation reaction calculations using a scripting language; S5, adjusting the cutoff radius. This method can quickly and accurately screen reactive atoms, avoid the occurrence of numerous binary ring structures, and yield more reasonable amorphous structures. The simulation process is simple and time-efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for simulating the growth of a silica aerogel structure. BACKGROUND

[0002] Silica aerogels belong to the largest class of high-porous inorganic aerogels. They were first introduced by Kistler in 1931 and even today, they are one of the most important and most studied nanostructured materials. They have outstanding properties such as very low thermal conductivity, very low density, high porosity and high surface area (useful as catalytic supports, Cherenkov detectors and adsorbents for organic and heavy metal pollutants in water and soil), low dielectric constant (useful in various electronic components), good optical properties, etc.

[0003] The special porous structure of aerogel materials is the key to determining their properties. The pores of aerogels have a clear microporous and mesoporous structure and have a multi-scale pore structure feature. This structural feature is formed by the hydrolysis and condensation reactions of multifunctional precursors in a solution environment. For silica-based aerogels, the precursors are mainly Si(OR)4 or R' n Si(OR) n-4 (n = 0-3, R' and R represent different types of organic functional groups, respectively) and the solution environment is mainly aqueous or alcoholic solution system. The reaction mechanism of aerogel formation is mainly that after the hydrolysis of the precursors, silanol substances such as Si(OH)4 or R' n -Si-(OR) n-4 are formed, which, after condensation, form a Si-O-Si main structure and gradually form a three-dimensional cross-linked network structure based on this. In this process, under suitable reaction conditions, first smaller nanosol particles are formed, then the sol particles agglomerate and gradually become cluster structures, and finally the network skeleton structure composed of nanoparticles is formed, and in the macroscopic form, it appears as a solid gel. At present, computer simulation has become an important complementary method for theoretical research and scientific experiments. On the one hand, computer simulation methods can study the structural features and performance characteristics of materials, explain experimental phenomena, and thus assist in the design of materials; on the other hand, various aggregation states of molecular systems can be constructed to predict their physical and chemical properties, thus providing new theoretical methods for material development.

[0004] The modeling process of the silicon aerogel system has a feature different from the molecular modeling of general systems, that is, the particularity of the three-dimensional network structure of amorphous. In most molecular simulation modeling processes, the simulation objects are covalent compound crystals, metals, or polymers with repeating units. The microstructures of most of the above substances are ordered. When modeling the above substances, existing modeling software packages can be used to construct them through some relatively simple repetitive operations, and the modeling difficulty is not high. However, silicon aerogel is a special disordered polymer that cannot define repeating units due to its amorphous structure. Therefore, in order to model it, the condensation reaction between various silanols must be simulated dynamically to obtain an actual structure close to nature and an effective model. In this process, the simulation and reduction of chemical reactions are the difficulties of molecular simulation. Therefore, the core of the work of molecular simulation of silicon aerogel is the modeling process. SUMMARY

[0005] The purpose of the present application is to solve the technical problems of the simulation process of the structure of the silica aerogel being relatively complicated, the simulation system being small, and the like, and to provide a growth simulation method for the structure of the silica aerogel, which can quickly and accurately screen out reactive atoms and avoid the occurrence of a large number of two-membered ring structures, and obtain a more reasonable amorphous structure, the simulation process is simple, and the time consumption is short.

[0006] In the research on the simulation of aerogel, the inventors found that although there are some references for simulating the structure of aerogel at present, the aerogel structure model constructed by the references has the defects of a relatively complicated simulation process, a small simulation system, and the like. The document "Multi-scale simulation and experimental study of silica-based aerogels" discloses a study on modeling of silica-based aerogels by using MS software. The document mainly aims at the simulation of RnSi(OH) 4-n The inventors know that the simulation of RnSi(OH) 4-n should be simpler than the simulation of Si(OH)4, but in actual application, water glass is usually hydrolyzed to generate Si(OH)4, and organosilicon source is hydrolyzed to generate RnSi(OH) 4-n , and the application of water glass is actually wider than that of organosilicon source.

[0007] In the research and test of simulating the original silicic acid molecule Si(OH)4, the inventors found that a large number of two-membered ring structures appeared in the model, but in fact, the generation of two-membered ring structures often needs a lot of energy, and such structures are rarely generated, which is inconsistent with the actual situation. The inventors also simulated the model of CH3Si(OH)3 in the aforementioned document and found that the number of two-membered ring structures appearing in the CH3Si(OH)3 model was indeed smaller than that in the Si(OH)4 model.

[0008] Therefore, in the simulation research of the growth simulation method of the silica aerogel structure generated from the orthosilicic acid molecule Si(OH)4, the inventors specially design the principle of generating the binary ring structure, constrain the emergence of a large number of binary ring structures, and optimize the simulation condensation reaction operation process, so that a silica aerogel structure more consistent with the actual is obtained.

[0009] The present application provides a growth simulation method of a silica aerogel structure, which comprises the following steps:

[0010] S1, establishing a molecular model of an orthosilicic acid molecule and performing energy minimization operation: using molecular simulation software to establish a molecular model of the orthosilicic acid molecule and to perform energy minimization operation on the structure of the orthosilicic acid molecule, so as to obtain an energy-optimized orthosilicic acid molecule structure;

[0011] S2, establishing an amorphous box: establishing an amorphous box containing at least two energy-optimized orthosilicic acid molecule structures;

[0012] S3, performing energy minimization and molecular dynamics relaxation operation on the amorphous box;

[0013] S4, performing simulation condensation reaction operation by using script language programming;

[0014] The structure obtained by step S3 operation is subjected to simulation condensation reaction operation, and the specific process is as follows:

[0015] ①Introducing reaction assumption conditions: limiting two molecules to only one condensation reaction;

[0016] ②Marking reaction atoms, the reaction atoms are Si atoms, H atoms and O atoms, marking the H atoms on the O-H atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; the O atoms connected by H atoms are marked as atom3, and the Si atoms connected by O atoms are marked as atom4;

[0017] ③Setting a cutoff radius, the initial value of the cutoff radius is set to

[0018] ④Measuring the distance d between the H and O atoms in any pair of H(atom1) and O(atom2) atom pairs in the structure obtained by step S3 operation; comparing the d with the cutoff radius,

[0019] If the distance d is less than or equal to the cut-off radius, a condensation reaction occurs to construct a cross-linking structure; the construction of the cross-linking structure is to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure in which the condensation reaction occurs, establish a new bond between O(atom1) and Si(atom4), and then saturate the H atom according to the coordination condition of each atom;

[0020] If the distance d is greater than the cut-off radius, no condensation reaction occurs, and no operation is performed;

[0021] S5, performing a molecular dynamics relaxation operation on the structure obtained in step S4;

[0022] S6, repeating steps S4 and S5 until the reaction degree reaches 30%-45% and stopping the reaction;

[0023] S7, setting the initial value of the cut-off radius as Then, steps S4 to S5 are repeated for 3 times.

[0024] S8, adjusting the cut-off radius from to wherein steps S4 to S5 are repeated for 3 times.

[0025] In the present application, the molecular simulation software can be a software commonly used in the field to perform molecular simulation, such as Material Studio software or Lammps software.

[0026] In step S1, the way of establishing the molecular model of the orthosilicic acid molecule is preferably to use the Visualizer module of the Material Studio software. The molecular model setting of the orthosilicic acid molecule generally includes setting 4 reactive OH connected to the Si atom; selecting COMPASS II to classify and charge the atoms;

[0027] In step S1, the way of performing the energy minimization operation on the structure of the orthosilicic acid molecule is preferably to use the Forcite module of the Material Studio software, wherein the optimization method is preferably selected as the Geometry Optimization method, the force field is preferably selected as the COMPASS II molecular force field, and the non-bonding interaction summation method is preferably selected as the Atom based method.

[0028] In step S2, the amorphous box is preferably constructed using the Amorphous Cell module of Material Studio software. The initial density of the liquid mixture is preferably set to 0.1 g / cm³. 3 -0.3g / cm 3 The COMPASS II force field is preferred for molecular force field, the Ewald method is preferred for Coulomb summation, and the Atom-based method is preferred for van der Waals summation.

[0029] In step S2, when constructing the amorphous box, the number of orthosilicic acid molecules can be increased as needed, with no upper limit. The more molecules there are, the longer the calculation time will be. Preferably, the number of molecules is controlled to not exceed 10,000.

[0030] In step S3, the energy minimization calculation of the amorphous box obtained in step S2 is preferably performed using the Forcite module in Material Studio software. Preferably, the optimization method is Geometry Optimization, the simulation system is NVT, and the nonbonded interaction summation method is Ewald. Alternatively, the optimization method is Smart Minimize, the molecular force field is COMPASS, and the nonbonded interaction summation method is Ewald.

[0031] In step S3, the molecular dynamics relaxation operation of the amorphous box obtained in step S2 is preferably performed using the Forcite module in Material Studio software; wherein, the molecular force field is preferably selected as COMPASS II molecular force field, the simulation system is preferably selected as NVT system, the nonbonding interaction summation method is preferably selected as Ewald nonbonding interaction summation method; the model temperature is preferably selected as 300K-500K, the time step is preferably selected as 0.1 femtosecond, the total simulation time is preferably selected as 30-100 picosecond, more preferably 50 picosecond; and the trajectory output interval is preferably selected as 500 steps.

[0032] In step S4, the scripting language is preferably Perl.

[0033] In step S4, the method of measuring the distance d between H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained by step S3 is preferably to use the Measure tool of the Visualizer module in Material Studio software.

[0034] In step S5, the molecular dynamics relaxation calculation is preferably performed using the Forcite module in Material Studio software. In the Forcite module, the force field is preferably selected as COMPASS II molecular force field, the simulation system is preferably selected as NVT system, the temperature cycling range is preferably selected as 450K, and the total simulation time of the molecular dynamics relaxation calculation is preferably selected as 100 picoseconds.

[0035] In step S8, the gradually increasing radius number is preferably...

[0036] As is known to those skilled in the art, MS software is short for Material Studio software.

[0037] In this invention, the simulated condensation reaction calculation in step S4 involves hydroxyl groups and has no other requirements or restrictions on the chemical environment surrounding the groups. Therefore, it can be used to construct any cross-linked network structure formed by dehydration condensation reaction.

[0038] In simulating cross-linking reactions, existing technologies include increasing the cutoff radius, which gradually increases from small to large. However, this sometimes leads to a problem: some high-density parts in the simulation box tend to agglomerate, resulting in the final output structure being individual blocky structures rather than a large cross-linked network. This application addresses this issue by first setting the cutoff radius to... The reaction is stopped when the degree of reaction reaches 30%-45%, and then the cutoff radius is adjusted from... Gradually increase to The model structure output by the solution in this application is closer to a cross-linked network structure. With slight modifications based on the principles of this invention, it can be applied to the construction of amorphous cross-linked network structures formed by any type of cross-linking reaction.

[0039] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0040] The reagents and raw materials used in this invention are all commercially available.

[0041] Beneficial technical effects of the present invention:

[0042] 1. The growth simulation method for silica aerogel structures of the present invention is characterized by its simple operation, rapid and accurate screening of reactive atoms, avoiding the formation of numerous binary ring structures, and yielding more reasonable amorphous structures. The simulation process is simple and time-saving; it utilizes a scripting language to allow the computer to repeat the process automatically, eliminating the need for manual repetition and saving significant time. This method also features adjustable component range; the system has no limit on the number of orthosilicic acid molecules, which can be arbitrarily set, with the upper limit limited by the computer's computational capabilities.

[0043] 2. The growth simulation method for silica aerogel structures of the present invention has the advantage of wide applicability and can be used to construct amorphous cross-linked network structures formed by any dehydration condensation reaction. It is worth noting that the construction of amorphous structures is much more complex than the construction of ordered structures. Therefore, with slight modifications based on the present invention, it can be applied to the construction of cross-linked structures formed by any type of cross-linking reaction. Attached Figure Description

[0044] Figure 1 A diagram illustrating the bonding process of a condensation reaction between two orthosilicic acid molecules.

[0045] Figure 2 Example 1: Flowchart of the construction process of amorphous silica aerogel structure.

[0046] Figure 3 Comparative Example 1: A schematic diagram of a slice representing the simulated cross-linked structure model of orthosilicic acid molecules.

[0047] Figure 4 Comparative Example 2: A schematic diagram of a slice of a simulated cross-linked structure model of orthosilicic acid molecules.

[0048] Figure 5 Comparative Example 3: A schematic diagram of a slice representing the simulated cross-linked structure model of orthosilicic acid molecules.

[0049] Figure 6 Comparative Example 7: A schematic diagram of a slice representing the simulated cross-linked structure model of orthosilicic acid molecules.

[0050] Figure 7 TEM image of aerogel prepared in the laboratory.

[0051] Figure 8 Example 1: A schematic diagram of the simulated cross-linked structure model of orthosilicic acid molecules.

[0052] Figure 9 Comparative Example 4: A schematic diagram of a slice representing the simulated cross-linked structure model of orthosilicic acid molecules.

[0053] Figure 10 Comparative Example 5: A schematic diagram of the simulated cross-linked structure model of orthosilicic acid molecules.

[0054] Figure 11 Comparative Example 6: A schematic diagram of a slice representing the simulated cross-linked structure model of orthosilicic acid molecules.

[0055] Figure 12 Comparative Example 1: Flowchart of the construction process of the amorphous silica aerogel structure. Detailed Implementation

[0056] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0057] The Material Studio software used in the embodiments and comparative examples of this invention was purchased from Beijing Chuangteng Technology Co., Ltd., version number 2017 [17.1.0.48], which includes the Visualize, Forcite, Amorphous Cell modules and Compass molecular force field.

[0058] Example 1:

[0059] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a cutoff radius set at a reaction extent of less than 45%. When the degree of reaction is greater than 45%, the cutoff radius is changed from Increase to The specific steps are as follows:

[0060] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software; four reactive OH groups were set to be attached to the Si atom; and COMPASS II was used to classify and charge the atoms. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and Atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0061] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.2 g / cm³. 3 The molecular force field was selected from the COMPASS II force field, the Coulomb summation was performed using the Ewald method, and the van der Waals summation was performed using the Atom-based method.

[0062] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method of the Forcite module are selected. For energy minimization, the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method are selected. For molecular dynamics relaxation, COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method are selected. The temperature is 300K, the time step is 0.1 femtoseconds, the total simulation time is 100 picoseconds, and the trajectory output interval is 500 steps.

[0063] S4. Use Perl programming language to perform simulation of condensation reaction calculations;

[0064] The structure obtained in step S3 is subjected to a simulated condensation reaction calculation. The specific process is as follows:

[0065] ① Introduce reaction assumptions: restrict the two molecules to undergo only one condensation reaction;

[0066] ② Label the reaction atoms, which are Si atoms, H atoms and O atoms. Label the H atoms on the OH atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; label the O atoms connected to the H atoms as atom3, and the Si atoms connected to the O atoms as atom4.

[0067] ③ Set the cutoff radius; the initial value of the cutoff radius is set to...

[0068] ④ Use the Measure tool in the Visualizer module of MS software to measure the distance d between the H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3; compare d with the cutoff radius.

[0069] If the distance d is less than or equal to the cutoff radius, a condensation reaction occurs, and a cross-linked structure is constructed. The construction of the cross-linked structure is carried out by using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0070] If the distance d is greater than the cutoff radius, no condensation reaction occurs, and no operation is performed.

[0071] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, the force field is selected as COMPASS II molecular force field, the system is selected as NVT system, the temperature cycling range is selected as 450K, and the total simulation time for molecular dynamics calculations at this temperature is selected as 100 picoseconds.

[0072] S6. Repeat steps S4 and S5 until the reaction reaches 30%-45% and then stop the reaction.

[0073] S7. Set the initial value of the cutoff radius to... Then repeat steps S4 to S6, repeating 3 times;

[0074] S8. Adjust the cutoff radius from Gradually increase to Steps S4 to S6 are repeated, with each cutoff radius repeated 3 times, and the number of radii gradually increasing. End the reaction.

[0075] Figure 2 This is a flowchart of the construction process of the amorphous silica aerogel structure in Example 1.

[0076] The output structure is cut into cuboid blocks, and the cuboid blocks are then projected and processed in grayscale. The results are as follows: Figure 8 As shown, Figure 8 The actual size is 17.5*17.5 nm. Upon examination, the aerogel structure obtained from the simulated condensation reaction showed no binary ring structure, and the Si-O bond length was approximately [missing information]. The values ​​are approximately consistent with experimental values. Figure 1 A diagram illustrating the bonding process of a condensation reaction between two orthosilicic acid molecules. Simultaneously, the aerogel structure simulated in Example 1 is also shown. Figure 8 Compared with the aerogel TEM image taken in the laboratory ( Figure 7 The comparison revealed that the simulated output structure was consistent with the actual structure, thus proving that this method of simulating the growth of silica aerogel particles is effective and reasonable.

[0077] Comparative Example 1

[0078] A method for simulating the growth of silica aerogel particles, using 1000 orthosilicic acid atoms, with a set minimum cutoff radius of... Maximum cutoff radius is For example, the specific steps are as follows:

[0079] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and Atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0080] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 1000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.2 g / cm³. 3 The molecular force field is selected from COMPASS II force field, the Coulomb summation is selected from Ewald method, and the van der Waals summation is selected from Atom based method;

[0081] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, select the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method from the Forcite module. For energy minimization, select the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method. For molecular dynamics relaxation, select COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method. The temperature is set to 300 K, the time step to 0.1 femtoseconds, the total simulation time to 100 picoseconds, and the trajectory output interval to 500 steps.

[0082] S4. Simulate the condensation reaction using a script; set the initial value of the cutoff radius to... During step S4, the cutoff radius remains unchanged; the distance d between any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3 is measured using the Measure tool of the Visualizer module in MS software; the O atom connected to the H atom is denoted as atom3, and the Si atom connected to the O atom is denoted as atom4;

[0083] When the radius d between H and O atoms is less than or equal to D, and the H and O atoms come from different orthosilicic acid atoms, a condensation reaction occurs to construct a cross-linked structure. The construction of the cross-linked structure involves using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0084] When the distance d between H and O atoms is greater than D, no condensation reaction occurs and no operation is performed.

[0085] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, select COMPASS II molecular force field for the force field, NVT system for the system, 450K for the temperature cycling range, and 100 picoseconds for the total simulation time of the molecular dynamics calculation at this temperature.

[0086] S6. Repeat steps S4 and S5 until the loop count reaches 5 times;

[0087] S7. Compare the current cutoff radius with the maximum cutoff radius. If the size is less than the maximum cutoff radius, then add to the original cutoff radius. Then repeat steps S4 and S5 until the loop count reaches 3 times, then proceed to step 7 for judgment; if it is greater than the maximum cutoff radius... Then the program will end.

[0088] Figure 12 This is the flowchart for this comparative scheme. The output structure is cut into cuboid blocks, and the results of projection and grayscale processing of the cuboid blocks are as follows. Figure 3 As shown, Figure 3 The actual size is 8*8nm, compared to Figure 8 It can be seen Figure 8 The aerogel structure obtained by simulating the condensation reaction and the TEM image taken in the laboratory ( Figure 7 More consistent.

[0089] Comparative Example 2

[0090] A method for simulating the growth of silica aerogel particles, using 8000 orthosilicic acid atoms, with a set minimum cutoff radius of... Maximum cutoff radius is For example, the specific steps are as follows:

[0091] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and Atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0092] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 8000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.3 g / cm³. 3 The molecular force field is selected from COMPASS II force field, the Coulomb summation is selected from Ewald method, and the van der Waals summation is selected from Atom based method;

[0093] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, select the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method from the Forcite module. For energy minimization, select the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method. For molecular dynamics relaxation, select COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method. The temperature is set to 450 K, the time step to 0.1 femtoseconds, the total simulation time to 50 picoseconds, and the trajectory output interval to 500 steps.

[0094] S4. Simulate the condensation reaction using a script; set the initial value of the cutoff radius to... During step S4, the cutoff radius remains unchanged; the distance d between any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3 is measured using the Measure tool of the Visualizer module in MS software; the O atom connected to the H atom is denoted as atom3, and the Si atom connected to the O atom is denoted as atom4;

[0095] When the radius d between H and O atoms is less than or equal to D, and the H and O atoms come from different orthosilicic acid atoms, a condensation reaction occurs to construct a cross-linked structure. The construction of the cross-linked structure involves using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0096] When the distance d between H and O atoms is greater than D, no condensation reaction occurs and no operation is performed.

[0097] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, select COMPASS II molecular force field for the force field, NVT system for the system, 450K for the temperature cycling range, and 100 picoseconds for the total simulation time of the molecular dynamics calculation at this temperature.

[0098] S6. Repeat steps S4 and S5 until the loop count reaches 4 times;

[0099] S7. Compare the current cutoff radius with the maximum cutoff radius. If the size is less than the maximum cutoff radius, then add to the original cutoff radius. Then repeat steps S4 and S5 until the loop count reaches 3 times, then proceed to step 7 for judgment; if it is greater than the maximum cutoff radius... Then the program will end.

[0100] The output structure is cut into cuboid blocks, and the cuboid blocks are then projected and processed in grayscale. The results are as follows: Figure 4 As shown, Figure 4 The actual size is 16.2*16.2nm, compared to Figure 8 It can be seen Figure 8 The aerogel structure obtained by simulating the condensation reaction and the TEM image taken in the laboratory ( Figure 7 More consistent.

[0101] Comparative Example 3

[0102] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a set minimum cutoff radius of... Maximum cutoff radius is For example, the specific steps are as follows:

[0103] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and Atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0104] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.3 g / cm³. 3 The molecular force field is selected from COMPASS II force field, the Coulomb summation is selected from Ewald method, and the van der Waals summation is selected from Atom based method;

[0105] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, select the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method from the Forcite module. For energy minimization, select the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method. For molecular dynamics relaxation, select COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method. The temperature is set to 500 K, the time step to 0.1 femtoseconds, the total simulation time to 30 picoseconds, and the trajectory output interval to 500 steps.

[0106] S4. Simulate the condensation reaction using a script; set the initial value of the cutoff radius to... During step S4, the cutoff radius remains unchanged; the distance d between any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3 is measured using the Measure tool of the Visualizer module in MS software; the O atom connected to the H atom is denoted as atom3, and the Si atom connected to the O atom is denoted as atom4;

[0107] When the radius d between H and O atoms is less than or equal to D, and the H and O atoms come from different orthosilicic acid atoms, a condensation reaction occurs to construct a cross-linked structure. The construction of the cross-linked structure involves using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0108] When the distance d between H and O atoms is greater than D, no condensation reaction occurs and no operation is performed.

[0109] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, select COMPASS II molecular force field for the force field, NVT system for the system, 450K for the temperature cycling range, and 100 picoseconds for the total simulation time of the molecular dynamics calculation at this temperature.

[0110] S6. Repeat steps S4 and S5 until the loop count reaches 2 times;

[0111] S7. Compare the current cutoff radius with the maximum cutoff radius. If the size is less than the maximum cutoff radius, then add to the original cutoff radius. Then repeat steps S4 and S5 until the loop count reaches 3 times, then proceed to step 7 for judgment; if it is greater than the maximum cutoff radius... Then the program will end.

[0112] The output structure is cut into small rectangular blocks, and the results of projection and grayscale processing of the rectangular blocks are as follows: Figure 5 As shown, Figure 5 The actual size is 17.5*17.5nm, compared to Figure 8 It can be seen Figure 8 The aerogel structure obtained by simulating the condensation reaction and the TEM image taken in the laboratory ( Figure 7 More consistent.

[0113] Comparative Example 4

[0114] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a set reaction degree of less than 15%, has a minimum cutoff radius of [missing information]. When the degree of reaction is greater than 15%, the minimum cutoff radius is changed from Increase to The specific steps are as follows:

[0115] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and Atom-based nonbonded interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0116] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.2 g / cm³. 3 The molecular force field was selected from the COMPASS II force field, the Coulomb summation was performed using the Ewald method, and the van der Waals summation was performed using the Atom-based method.

[0117] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method of the Forcite module are selected; for energy minimization, the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method are selected; for molecular dynamics relaxation, COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method are selected. The temperature is 300K, the time step is 0.1 femtoseconds, the total simulation time is 100 picoseconds, and the trajectory output interval is 500 steps.

[0118] S4. Use Perl programming language to simulate the "condensation reaction" operation;

[0119] The structure obtained in step S3 is subjected to a simulated "condensation reaction" calculation, the specific process of which is as follows:

[0120] ① Introduce reaction assumptions: restrict the two molecules to undergo only one condensation reaction;

[0121] ② Label the reaction atoms, which are Si atoms, H atoms and O atoms. Label the H atoms on the OH atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; label the O atoms connected to the H atoms as atom3, and the Si atoms connected to the O atoms as atom4.

[0122] ③ Set the cutoff radius; the initial value of the cutoff radius is set to...

[0123] ④ Measure the distance d between H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained in step S3 using the Measure tool of the Visualizer module in MS software; compare the distance d with the cutoff radius.

[0124] If the distance d is less than or equal to the cutoff radius, a condensation reaction occurs, and a cross-linked structure is constructed. The construction of the cross-linked structure is carried out by using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure where the condensation reaction occurs, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0125] If the distance d is greater than the cutoff radius, no condensation reaction occurs, and no operation is performed;

[0126] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, the force field is selected as COMPASS II molecular force field, the system is selected as NVT system, the temperature cycling range is selected as 450K, and the total simulation time for molecular dynamics calculations at this temperature is selected as 100 picoseconds.

[0127] S6. Repeat steps S4 and S5 until the reaction reaches 15% and then stop the reaction.

[0128] S7. Set the initial value of the cutoff radius to... Then repeat steps S4 to S6, repeating 3 times;

[0129] S8. Adjust the cutoff radius from Gradually increase to Steps S4 to S6 are repeated, with each cutoff radius repeated 3 times. The number of progressively increasing radii is... End the reaction.

[0130] The output structure is cut into cuboid blocks, and the cuboid blocks are then projected and processed in grayscale. The results are as follows: Figure 9 As shown, Figure 9 The actual scale is 17.5*17.5nm. It can be clearly seen that the simulated structure output by this method is a dispersed block structure. The orthosilicic acid molecules failed to form a cross-linked network through condensation reaction, which is different from the aerogel TEM image taken in the laboratory. Figure 7 (This does not match.)

[0131] Comparative Example 5 (reaction rate 60%)

[0132] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a cutoff radius set when the degree of reaction is less than 60%. When the degree of reaction is greater than 60%, the cutoff radius is changed from Increase to The specific steps are as follows:

[0133] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0134] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.2 g / cm3, the molecular force field is selected from the COMPASS II force field, the Coulomb summation is performed using the Ewald method, and the van der Waals summation is performed using the Atom-based method.

[0135] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method of the Forcite module are selected. For energy minimization, the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method are selected. For molecular dynamics relaxation, COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method are selected. The temperature is 300K, the time step is 0.1 femtoseconds, the total simulation time is 100 picoseconds, and the trajectory output interval is 500 steps.

[0136] S4. Use Perl programming language to perform simulation of condensation reaction calculations;

[0137] The structure obtained in step S3 is subjected to a simulated condensation reaction calculation. The specific process is as follows:

[0138] ① Introduce reaction assumptions: restrict the two molecules to undergo only one condensation reaction;

[0139] ② Label the reaction atoms, which are Si atoms, H atoms and O atoms. Label the H atoms on the OH atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; label the O atoms connected to the H atoms as atom3, and the Si atoms connected to the O atoms as atom4.

[0140] ③ Set the cutoff radius; the initial value of the cutoff radius is set to...

[0141] ④ Measure the distance d between H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained in step S3 using the Measure tool of the Visualizer module in MS software; compare the distance d with the cutoff radius.

[0142] If the distance d is less than or equal to the cutoff radius, a condensation reaction occurs, and a cross-linked structure is constructed. The construction of the cross-linked structure is carried out by using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure where the condensation reaction occurs, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0143] If the distance d is greater than the cutoff radius, no condensation reaction occurs, and no operation is performed;

[0144] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, the force field is selected as COMPASS II molecular force field, the system is selected as NVT system, the temperature cycling range is selected as 450K, and the total simulation time for molecular dynamics calculations at this temperature is selected as 100 picoseconds.

[0145] S6. Repeat steps S4 and S5 until the reaction reaches 60%;

[0146] S7. Set the initial value of the cutoff radius to... Then repeat steps S4 to S6, repeating 3 times;

[0147] S8. Adjust the cutoff radius from Gradually increase to Steps S4 to S6 are repeated, with each cutoff radius repeated 3 times. The number of progressively increasing radii is... End the reaction.

[0148] Figure 10 This is a partial structural diagram of the output of this scheme. In the output model, the Si-O long bonds are approximately... The left and right sides result in the ligaments of the cross-linked network being thinner and longer, which does not match the actual structure.

[0149] Comparative Example 6 (Comparative Example of a Binary Ring)

[0150] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a set minimum cutoff radius of... Maximum cutoff radius is For example, the specific steps are as follows:

[0151] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0152] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.2 g / cm3, the molecular force field is selected from the COMPASS II force field, the Coulomb summation is performed using the Ewald method, and the van der Waals summation is performed using the Atom-based method.

[0153] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method of the Forcite module are selected. For energy minimization, the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method are selected. For molecular dynamics relaxation, COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method are selected. The temperature is 300K, the time step is 0.1 femtoseconds, the total simulation time is 100 picoseconds, and the trajectory output interval is 500 steps.

[0154] S4. Use Perl programming language to perform simulation of condensation reaction calculations;

[0155] The structure obtained in step S3 is subjected to a simulated condensation reaction calculation. The specific process is as follows:

[0156] ① Label the reacting atoms, which are Si atoms, H atoms and O atoms. Label the H atoms on the OH atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; label the O atoms connected to the H atoms as atom3, and the Si atoms connected to the O atoms as atom4.

[0157] ② Set the cutoff radius; the initial value of the cutoff radius is set to...

[0158] ③ Measure the distance d between H and O atoms in any pair of H(atom1) and O(atom2) atoms in the structure obtained in step S3 using the Measure tool of the Visualizer module in MS software; compare the distance d with the cutoff radius.

[0159] If the distance d is less than or equal to the cutoff radius, a condensation reaction occurs, and a cross-linked structure is constructed. The construction of the cross-linked structure is carried out by using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure where the condensation reaction occurs, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0160] If the distance d is greater than the cutoff radius, no condensation reaction occurs, and no operation is performed;

[0161] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, the force field is selected as COMPASS II molecular force field, the system is selected as NVT system, the temperature cycling range is selected as 450K, and the total simulation time for molecular dynamics calculations at this temperature is selected as 100 picoseconds.

[0162] S6. Repeat steps S4 and S5 until the loop count reaches 5 times.

[0163] S7. Compare the current cutoff radius with the maximum cutoff radius. If the size is less than the maximum cutoff radius, then add to the original cutoff radius. Then repeat steps S4 and S5 until the loop count reaches 3 times, then proceed to step 7 for judgment; if it is greater than the maximum cutoff radius... Then the program will end.

[0164] This method does not incorporate the assumption that two molecules can only undergo a single condensation reaction, resulting in a large number of binary ring structures appearing in the final simulated output, such as... Figure 11 As shown. The formation of binary ring structures requires a large amount of activation energy, so binary ring structures are rarely observed in actual experiments. Therefore, the structural model output by this method does not match reality.

[0165] Comparative Example 7 (Comparative Example of the Truncation Scheme)

[0166] A method for simulating the growth of silica aerogel particles, using 10,000 orthosilicic acid atoms, with a set cutoff radius of... The loop is repeated 10 times. The specific steps are as follows:

[0167] S1. A molecular model of the hydrolyzed orthosilicic acid molecule was established using the Visualizer module in MS software. The model was then used to classify and charge the atoms using COMPASS II. The energy minimization calculation of the orthosilicic acid molecule structure was performed using the Forcite module in MS software. In the Forcite module, the Geometry Optimization method, COMPASS II molecular force field, and atom-based nonbonding interaction summation method were selected to obtain the energy-optimal orthosilicic acid molecule structure.

[0168] S2. Using the Amorphous Cell module in MS software, construct an amorphous box containing 10,000 orthosilicic acid molecules. The initial density of the liquid mixture is set to 0.3 g / cm3, the molecular force field is selected from the COMPASS II force field, the Coulomb summation is performed using the Ewald method, and the van der Waals summation is performed using the Atom-based method.

[0169] S3. Using the Forcite module in MS software, perform energy minimization and molecular dynamics relaxation calculations on the S2 amorphous box. For energy minimization, the Geometry Optimization method, NVT system, and Ewald nonbonding interaction summation method of the Forcite module are selected. For energy minimization, the Smart Minimize method, COMPASS molecular force field, and Ewald nonbonding interaction summation method are selected. For molecular dynamics relaxation, COMPASS II molecular force field, NVT system, and Ewald nonbonding interaction summation method are selected. The temperature is 500K, the time step is 0.1 femtoseconds, the total simulation time is 30 picoseconds, and the trajectory output interval is 500 steps.

[0170] S4. Use a script to simulate the condensation reaction; set the initial value of the cutoff radius to... During step S4, the cutoff radius remains unchanged; the distance d between any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3 is measured using the Measure tool of the Visualizer module in MS software; the O atom connected to the H atom is denoted as atom3, and the Si atom connected to the O atom is denoted as atom4;

[0171] When the radius d between H and O atoms is less than or equal to D, and the H and O atoms come from different orthosilicic acid atoms, a condensation reaction occurs to construct a cross-linked structure. The construction of the cross-linked structure involves using the Visualizer module of MS software to delete the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, and to establish new bonds between O(atom1) and Si(atom4). Then, H atoms are saturated according to the coordination of each atom.

[0172] When the distance d between H and O atoms is greater than D, no condensation reaction occurs and no operation is performed.

[0173] S5. Perform molecular dynamics relaxation calculations using the Forcite module in MS software; perform molecular dynamics relaxation on the structure from step S4 using the Forcite module in MS software. In the Forcite module, the force field is selected as COMPASS II molecular force field, the system is selected as NVT system, the temperature cycling range is selected as 450K, and the total simulation time for molecular dynamics calculations at this temperature is selected as 100 picoseconds.

[0174] S6. Compare the current loop count with the set loop count. If the loop count is less than 10, repeat steps S4 and S5. If the loop count is greater than 10, end the program.

[0175] The output structure is cut into small rectangular blocks, and the results of projection and grayscale processing of the rectangular blocks are as follows: Figure 6 As shown, Figure 6 The actual size is 17.5*17.5nm. It can be clearly seen that... Figure 6 and Figure 3 , Figure 4 , Figure 5 and Figure 8 There are significant differences. Figure 6 The aerogel structure has a narrower cross-section, which is consistent with the electron micrograph of the aerogel prepared in the laboratory. Figure 7 The differences are significant, therefore the method used to construct the model in Comparative Example 4 is not very reasonable. The aerogel structure output by changing the cutoff radius during the "simulated cross-linking condensation" operation is more reasonable than the aerogel structure output by fixing the cutoff radius.

[0176] In summary, the method for simulating the growth of silica aerogel particles proposed in this invention, through molecular structure construction, energy minimization, structural mixing calculation, energy minimization and molecular dynamics relaxation calculation under 200-500K temperature conditions, simulated condensation reaction calculation, and molecular dynamics relaxation calculation under 450K temperature cycling, by limiting two molecules to only one condensation reaction, specifically changing the cutoff radius calculation, and appropriately controlling the reaction degree of the simulated condensation reaction calculation, avoids the appearance of a large number of binary rings and constructs a model structure that is more similar to the aerogel structure prepared in the laboratory.

Claims

1. A method for simulating the growth of silica aerogel structures, characterized in that, It includes the following steps: S1. Establishing a molecular model of orthosilicic acid and performing energy minimization calculations: Using molecular simulation software, a molecular model of the orthosilicic acid molecule is established and an energy minimization calculation is performed on the structure of the orthosilicic acid molecule to obtain the energy-optimal orthosilicic acid molecule structure. S2. Construct an amorphous box: Construct an amorphous box containing at least two of the energy-optimal orthosilicic acid molecular structures; S3. Perform energy minimization and molecular dynamics relaxation calculations on the amorphous box; S4. Simulate condensation reaction calculations using scripting language programming; The structure obtained in step S3 is subjected to a simulated condensation reaction calculation. The specific process is as follows: ① Introduce reaction assumptions: restrict the two molecules to undergo only one condensation reaction; ② Label the reaction atoms, which are Si atoms, H atoms and O atoms. Label the H atoms on the OH atoms from different orthosilicic acid molecules as atom1, and the O atoms as atom2; H atoms bonded to O atoms are denoted as atom3, and O atoms bonded to Si atoms are denoted as atom4; ③ Set the cutoff radius, the initial value of which is set to 4. ; ④ Measure the distance d between the H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained from step S3; compare the distance d with the cutoff radius. If the distance d is less than or equal to the cutoff radius, a condensation reaction occurs, and a cross-linked structure is constructed. The construction of the cross-linked structure involves deleting the molecular bonds of H(atom1)-O(atom3) and O(atom2)-Si(atom4) in the structure that has undergone the condensation reaction, establishing a new bond between O(atom1)+ and Si(atom4), and then saturating H atoms according to the coordination of each atom. If the distance d is greater than the cutoff radius, no condensation reaction occurs, and no operation is performed; S5. Perform molecular dynamics relaxation calculations on the structure obtained in step S4. S6. Repeat steps S4 and S5 until the reaction reaches 30%-45% and then stop the reaction. S7. Set the initial value of the cutoff radius to 2. Then repeat steps S4 to S5, repeating 3 times; S8. Adjust the cutoff radius from 2 Gradually increase to 6 Steps S4 to S6 are repeated 3 times.

2. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The molecular simulation software is Material Studio.

3. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The molecular model of the orthosilicic acid molecule is established using the Visualizer module of Material Studio software. The molecular model settings of the orthosilicic acid molecule include setting four reactive OH groups attached to the Si atom; and selecting COMPASS II to classify and charge its atoms.

4. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The energy minimization calculation for the structure of the orthosilicic acid molecule is performed using the Forcite module of Material Studio software.

5. The method for simulating the growth of silica aerogel structures as described in claim 4, characterized in that, In the Forcite module, the optimization method selected is Geometry Optimization. And / or, in the Forcite module, the force field is selected as COMPASS II molecular force field; And / or, in the Forcite module, the non-bond summation method is selected as an Atom-based method.

6. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The amorphous box was constructed using the Amorphous Cell module of Material Studio software.

7. The method for simulating the growth of silica aerogel structures as described in claim 6, characterized in that, In the Amorphous Cell module, the initial density of the liquid mixture is set to 0.1 g / cm³. 3 -0.3 g / cm 3 ; And / or, in the Amorphous Cell module, the molecular force field is selected as the COMPASS II force field; And / or, in the Amorphous Cell module, the Coulomb summation selects the Ewald method; And / or, in the Amorphous Cell module, the van der Waals action selects the Atom-based method for summation.

8. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The energy minimization calculation for the amorphous box obtained in step S2 is performed using the Forcite module in Material Studio software.

9. The method for simulating the growth of silica aerogel structures as described in claim 8, characterized in that, In the Forcite module, the optimization method selected is Geometry Optimization. And / or, in the Forcite module, the simulation system is selected as the NVT system; And / or, in the Forcite module, the nonbonded action summation method is selected as the Ewald nonbonded action summation method.

10. The method for simulating the growth of silica aerogel structures as described in claim 8, characterized in that, In the Forcite module, the Smart Minimize method is selected as the optimization method. And / or, in the Forcite module, the molecular force field is selected as COMPASS molecular force field; And / or, in the Forcite module, the nonbonded action summation method is selected as the Ewald nonbonded action summation method.

11. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, The molecular dynamics relaxation operation of the amorphous box obtained in step S2 is performed using the Forcite module in Material Studio software.

12. The method for simulating the growth of silica aerogel structures as described in claim 11, characterized in that, In the Forcite module, the molecular force field is selected as COMPASS II molecular force field; And / or, in the Forcite module, the simulation system is selected as the NVT system; And / or, in the Forcite module, the nonbonded action summation method is selected as the Ewald nonbonded action summation method.

13. The method for simulating the growth of silica aerogel structures as described in claim 11, characterized in that, In the Forcite module, the model temperature is selected as 300 K-500 K; And / or, in the Forcite module, the time step is selected as 0.1 femtoseconds; And / or, in the Forcite module, the total simulation time is selected to be 30-100 picoseconds; And / or, in the Forcite module, the trajectory output interval is selected as 500 steps.

14. The method for simulating the growth of silica aerogel structures as described in claim 11, characterized in that, In the Forcite module, the total simulation time is set to 50 picoseconds.

15. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, In step S4, the scripting language is Perl. And / or, the distance d between H and O atoms in any pair of H (atom1) and O (atom2) atoms in the structure obtained by the measurement step S3 is measured using the Measure tool of the Visualizer module in Material Studio software.

16. The method for simulating the growth of silica aerogel structures as described in claim 1, characterized in that, In step S5, the molecular dynamics relaxation operation is performed using the Forcite module in Material Studio software.

17. The method for simulating the growth of silica aerogel structures as described in claim 16, characterized in that, In step S5, in the Forcite module, the force field is selected as COMPASS II molecular force field, the simulation system is selected as NVT system, the temperature cycling range is selected as 450 K, and the total simulation time of the molecular dynamics relaxation operation is selected as 100 picoseconds. And / or, the number of progressively increasing radii is 1. .

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