A method for constructing a full-atom numerical model of calcium silicate hydrate (C-S-H)

Abstract

This invention discloses a method for constructing a fully atomic numerical model of hydrated calcium silicate (C-S-H), which overcomes the anisotropy limitations of traditional crystal models caused by their ordered layered structure. The process includes: constructing a prepolymer model composed of tricalcium silicate / dicalcium silicate / water molecules based on molecular dynamics; optimizing the molecular configuration to correct the Dreiding force field based on density functional theory; and constructing an amorphous C-S-H model with a three-dimensional continuous, randomly cross-linked network structure by controlling the stepwise polymerization of silicon-oxygen tetrahedra through a Perl cross-linking program based on the C-S-H hydration reaction process. This model reproduces the amorphous characteristics and macroscopic isotropy of C-S-H gel. This invention provides a numerical model foundation closer to the real state of matter for exploring the microstructure and performance regulation of cement-based materials at the atomic scale, and provides theoretical support for revealing the cement hydration process and its intrinsic mechanism.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of computational materials science and civil engineering materials, specifically to a novel method for constructing a fully atomic numerical model of hydrated calcium silicate (CSH) by combining molecular dynamics and density functional theory. Background Technology

[0002] Cement, as an important inorganic cementitious material, plays an indispensable role in the construction of key infrastructure such as buildings, transportation, civil engineering, and water conservancy. Its macroscopic mechanical properties and long-term durability directly depend on the physicochemical properties and microstructural evolution of its hydration products (mainly calcium silicate hydrate: CSH). Therefore, in-depth understanding of the cement hydration process and the characteristics of its product CSH is of great significance for ensuring the safety and service life of engineering structures.

[0003] Traditional experimental methods for studying cement hydration mechanisms and microstructures are often limited by sample preparation and characterization techniques, making it difficult to accurately capture the dynamic evolution of CSH structures at the microscale. Furthermore, these methods are time-consuming and costly. In recent years, molecular simulations, with their unique advantage of being able to resolve material structures and dynamic processes at the atomic level, have gradually developed into an important computational tool for revealing the microscopic behavior of cement-based materials.

[0004] Among them, molecular dynamics is one of the most widely used methods in the field of molecular simulation. With its dynamic simulation characteristics, it has become a key means to study the microstructure evolution and performance correlation of CSH. In molecular simulation, constructing a numerical model that can accurately describe the system structure characteristics is an important prerequisite for ensuring the reliability of simulation results and the effectiveness of prediction. At present, the molecular models commonly used to characterize CSH are mainly based on ideal crystal structures, such as tobermorite and hydroxyl calcium silicate (Jennite).

[0005] Although these models provide important references for the study of cement materials, they have obvious structural limitations: they have a defined crystal structure and chain / layered topology, lacking the three-dimensional random cross-linked network structure that is common in real cement materials. Therefore, they usually exhibit significant anisotropy in simulations, which is fundamentally different from the long-range disordered, amorphous, and isotropic gel characteristics of real cement materials. This limits the applicability of the models in predicting the mechanical behavior, transport properties, and long-term evolution of real cement systems.

[0006] To address these technical problems, this application proposes a method for constructing a full-atom numerical model of calcium silicate hydrate (CSH). Summary of the Invention

[0007] The main objective of this invention is to provide a method for constructing a full-atom numerical model of calcium silicate hydrate (CSH). Based on the structural characteristics and chemical reaction pathways of CSH, a novel high-precision full-atom numerical model of calcium silicate hydrate (CSH) is constructed. This model possesses a three-dimensional continuous, randomly cross-linked amorphous network topology, which can more realistically reflect the amorphous structure and isotropic characteristics of cement hydration products. This provides a computational model that is closer to the real system for in-depth exploration of the microscopic properties and performance regulation of cement materials at the atomic scale, thereby solving the technical problems mentioned in the background art.

[0008] The present invention solves the above-mentioned technical problems by adopting the following technical solutions: A method for constructing a fully atomic numerical model of calcium silicate hydrate (CSH) involves the following steps executed via computer equipment: Based on molecular dynamics, a molecular model of tricalcium silicate / dicalcium silicate (C3S / C2S) was constructed using the Materials Studio software platform. Tricalcium silicate / dicalcium silicate (C3S / C2S) is the most important mineral for the formation of CSH in cement clinker. Using the Amorphous Cell module of the software platform, a CSH prepolymer model was established by randomly stacking water molecules into a tricalcium silicate / dicalcium silicate (C3S / C2S) molecular model based on the Monte Carlo method; The CSH prepolymer model was pre-optimized using the steepest descent method, and the interatomic interactions were described using the Dreiding force field. To improve the accuracy of the numerical model, density functional theory was used to perform geometric optimization on the molecular configuration involved in the CSH prepolymer model to obtain molecular structure parameters. These molecular structure parameters were used to verify and correct the specified key parameters in the original Dreiding force field, and the obtained corrected force field was defined as the Dreiding-CSH force field. Then, based on the Dreiding-CSH force field, the CSH prepolymer model was dynamically relaxed to obtain the initial configuration; Based on the initial configuration, a cross-linking program was written using molecular dynamics methods, and a CSH model with a three-dimensional cross-linked structure was constructed by simulating the CSH hydration reaction process. During this process, the crosslinking procedure can construct CSH models with different degrees of crosslinking (hydration) as needed.

[0009] Preferably, the CSH prepolymer model includes water molecules (H2O) and calcium ions (Ca). 2+ Silicon-oxygen tetrahedral SiO4 4-Furthermore, the initial packing density of the CSH prepolymer model can be set to 2.8–3.2 g / cm³. 3 .

[0010] Preferably, the CASTEP module based on the software platform uses density functional theory to perform geometric optimization of the silicon-oxygen tetrahedra and water molecules in the CSH prepolymer model. During the geometric optimization process: The exchange correlation energy is handled using the generalized gradient approximation (GGA) of the PBE form; The electron-nuclear interaction is described using the OTFG-ultrasoft pseudopotential; The optimization method is based on the LBFGS algorithm; Brillouin zones are sampled using a 4×4×4 k-point grid.

[0011] Preferably, the crosslinking program is written in Perl language to specify silicon atoms and oxygen atoms as the main bonding sites, wherein silicon atoms serve as the nucleation framework and the bonding radius is set to 3-8 Å. In this case, atomic interactions are described based on the Dreiding-CSH force field, and the simulation is carried out at room temperature and pressure.

[0012] Preferably, the crosslinking process includes the following steps: Step 1. Perform cross-linking bonding operation: Set the chemical bond formation to cross-linking of silicon-oxygen tetrahedral single cells into chains, generating silicon-oxygen tetrahedra with different degrees of hydroxylation; Step 2. After cross-linking, the conjugate gradient optimization algorithm is used to perform static optimization on silicon-oxygen tetrahedra with different degrees of hydroxylation, and kinetic relaxation is carried out under the NVT ensemble to provide optimized configurations for subsequent cross-linking. Step 3. Gradually increase the cross-linking radius until a branched CSH intermediate is formed; Step 4. Based on the configuration of the CSH intermediate, reset the silicon / oxygen atom bonding sites and set the program to allow self-crosslinking of chain-like CSH to form a network structure model; Step 5. For numerical models that have reached the preset degree of crosslinking, dynamic relaxation is performed under the NPT ensemble to finally complete the construction of a three-dimensional crosslinked structure CSH all-atom numerical model with the specified degree of crosslinking.

[0013] Furthermore, the CSH all-atom numerical model also verifies the isotropic or anisotropic characteristics exhibited by CSH with different degrees of crosslinking (i.e., hydration) in the macroscopic mechanical response based on the calculation of the material's elastic constants and analysis of mechanical properties. The mechanical property calculation is based on the constant strain method, and the maximum strain amplitude does not exceed 2‰.

[0014] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0015] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0016] As can be seen from the above technical solution, the present invention provides a method for constructing a full-atom numerical model of calcium silicate hydrate (CSH). Compared with the prior art, the present invention has the following advantages: 1. The model constructed in this invention can combine the molecular structure characteristics of materials and establish a CSH model with typical amorphous disorder and isotropic characteristics by simulating the hydration reaction process. It can also more accurately reflect the physical properties of the hydration product system, providing a more reliable numerical model for molecular dynamics simulation at the atomic scale and providing key support for revealing the cement hydration process and its intrinsic mechanism.

[0017] 2. This invention constructs CSH all-atom numerical models with different degrees of crosslinking through a stepwise crosslinking and site resetting strategy, and calculates mechanical parameters based on microscopic numerical methods, realizing the correlation analysis from microstructure to macroscopic mechanical response, and providing an important method for revealing the microstructural characteristics of cement materials with different degrees of hydration.

[0018] It should be understood that the descriptions in this section are not intended to identify key or essential features of embodiments of the invention, nor are they intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Of course, implementing any product of the invention does not necessarily require achieving all of the advantages described above simultaneously. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall process of the present invention; Figure 2 This is a schematic diagram of the molecular model structure of the C3S / C2S and CSH prepolymers of the present invention; Figure 3 The diagrams show the configurations and parameters of the silicon-oxygen tetrahedron and water molecule after the structural optimization of the present invention, wherein: (a) is a diagram showing the configuration and parameters of the silicon-oxygen tetrahedron, and (b) is a diagram showing the configuration and parameters of the water molecule; Figure 4This is a diagram illustrating the construction process of the three-dimensional randomly cross-linked CSH model of the present invention; Figure 5 The diagram shows a comparison of the Tobermorite model and the CSH model constructed in this invention, where: (a) is the front view and side view of the Tobermorite model, and (b) is the front view and side view of the CSH model constructed in this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] For details in the embodiments, please refer to Figures 1 to 5 .

[0022] like Figure 1 As shown, the method for constructing a full-atom numerical model of calcium silicate hydrate (CSH) proposed in this embodiment of the invention, based on the Materials Studio software platform, constructs a CSH model with a three-dimensional network structure by combining molecular dynamics and density functional theory, including the following steps: S1. Construct a C3S / C2S molecular model, and add an aqueous solution to establish a CSH prepolymer model, such as... Figure 2 As shown in the diagram. Specifically, the Amorphous Cell module is used, and water molecules are randomly packed into a C3S / C2S model based on the Monte Carlo method. The initial packing density of the model can be set to 2.8–3.2 g / cm³. 3 .

[0023] It's important to explain here that CSH is primarily formed from the hydration reaction of tricalcium silicate (C3S) and dicalcium silicate (C2S) in cement clinker. The main components of C3S / C2S are calcium oxide and silicon dioxide, which dissolve in water to form calcium ions (Ca). 2+ Silicon-oxygen tetrahedral SiO4 4- Then, cross-linking polymerization is used to generate CSH.

[0024] S2. The prepolymer structure is pre-optimized. The optimization method used here is the steepest descent method. At the same time, the Dreiding force field is used to describe the interatomic interaction during the optimization process. This force field has good applicability to inorganic material systems.

[0025] S3. Subsequently, in order to further improve the accuracy of the numerical model, density functional theory was used to perform geometric optimization on the molecular configuration involved in the prepolymer model, thereby obtaining the structural parameters of the relevant molecules, and based on this, the key parameters in the Dreiding force field were verified and corrected.

[0026] In the geometry optimization process, the CASTEP module was used to optimize the geometry of the silicon-oxygen tetrahedral cell and water molecules. During this calculation, the generalized gradient approximation (GGA) of PBE form was used to handle the exchange correlation energy, and the OTFG-ultrasoft pseudopotential was employed. The optimization method was based on the LBFGS algorithm. A 4×4×4 k-point grid was used for Brillouin zone sampling, and the energy convergence threshold for the self-consistent field (SCF) iteration was set to 10. -6 eV / atom, after structural optimization, the geometric parameters of the silicon-oxygen tetrahedron and water molecule are as follows: Figure 3 As shown.

[0027] Furthermore, it should be noted that the Dreiding force field is corrected using optimized molecular bond lengths and bond angles, where the Si-O bond length r = 1.624 Å, the HO bond length r = 0.971 Å, and the force constant K. r =700kcal / (mol·Å) 2 The O-Si-O bond angle θ = 109.428°, the HOH bond angle θ = 104.216°, and the force constant K θ =100kcal / (mol·rad) 2 The bond length stretching energy and bond angle bending energy were calculated using the Harmonic function (resonance form), and the corrected molecular force field was named Dreiding-CSH.

[0028] S4. Based on the modified Dreiding-CSH force field, the CSH prepolymer model is dynamically relaxed to provide an optimized initial configuration for the subsequent construction of the three-dimensional crosslinking model.

[0029] In the model construction, a CSH model with a three-dimensional cross-linked structure needs to be established through a cross-linking program based on the CSH hydration reaction process. The cross-linking program is written in Perl language, and silicon atoms and oxygen atoms are specified as the main bonding sites (silicon atoms as the nucleation framework) in the program. The bonding radius is 3 to 8 Å. At this time, the atomic interaction is described based on the Dreiding-CSH force field, and the simulation is carried out at room temperature and pressure.

[0030] It should be further explained that the model is established in two stages, such as... Figure 4 As shown, the details are as follows: The first stage is: silicon-oxygen tetrahedra form chain-like CSH through polymerization in aqueous solution.

[0031] In the first stage, chemical bond formation was defined as the cross-linking of silicon-oxygen tetrahedral single cells into chains, and the generation of silicon-oxygen tetrahedra with different degrees of hydroxylation. After cross-linking, the model was statically optimized (using a conjugate gradient optimization algorithm), and kinetic relaxation was performed under the NVT ensemble to provide optimized configurations for subsequent reactions. Subsequently, the bonding radius was gradually increased until branched CSH intermediates were formed.

[0032] The second stage involves the further polymerization of branched CSH intermediates to form a three-dimensional randomly cross-linked network structure.

[0033] In the second stage, based on the CSH intermediate model, the silicon / oxygen atom bonding sites are reset, and the program is configured to allow self-crosslinking of chain-like CSH. In this stage, the present invention can construct numerical models with different degrees of crosslinking according to the hydration reaction process to characterize CSH with different degrees of hydration.

[0034] Finally, for the numerical model that reaches the preset degree of crosslinking, a three-dimensional continuous and randomly crosslinked CSH all-atom numerical model is constructed by performing dynamic relaxation under the NPT ensemble.

[0035] Furthermore, this method analyzes the mechanical properties based on calculated material elastic constants, and uses this to examine the isotropic or anisotropic characteristics exhibited by CSH with different degrees of hydration in the macroscopic mechanical response. At this point, as... Figure 5 As shown, the calculation and analysis are carried out using the Tobermorite model and the CSH model constructed by this method as examples to ensure that the densities of the two models are basically consistent. The mechanical properties are calculated based on the constant strain method, and the maximum strain amplitude does not exceed 2‰.

[0036] At this point, through simulation calculations, the Young's modulus in three directions for the two models is obtained as shown in Table 1 below: Table 1: Comparison of Young's modulus results for different models

[0037] The calculation results in the table above show that the Tobermorite model exhibits significant differences in Young's modulus across the three directions, demonstrating clear anisotropic mechanical characteristics. This is mainly due to its well-defined crystal order and chain / layered topology. Specifically, the Tobermorite model exhibits a high modulus in the Y direction primarily due to strong covalent bonds, while in the X and Z directions, it is mainly maintained by weaker ionic bonds, hydrogen bonds, and van der Waals interactions, resulting in lower Young's moduli. Figure 5 As shown in (a).

[0038] The CSH model constructed in this invention exhibits similar Young's moduli in all three directions. This is due to its three-dimensional continuous, randomly cross-linked network structure, which more realistically reflects the amorphous structure and isotropic characteristics of CSH. Figure 5 As shown in (b).

[0039] In summary, this invention, based on molecular simulation technology, proposes a systematic method for constructing a fully atomic numerical model of hydrated calcium silicate (CSH) by simulating the cement hydration process. This method can provide a more realistic and reliable model foundation for a deeper understanding of the microscopic properties of cement-based materials at the atomic scale.

[0040] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0041] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0042] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute any of the calcium silicate hydrate CSH all-atom numerical model construction methods in the above embodiments.

[0043] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, an optical medium, or a semiconductor medium, etc.

[0044] It should be noted that this application focuses on protecting the construction method and related system flow of the CSH numerical model. The described embodiments are merely specific implementations of this application, but the scope of protection of the invention is not limited thereto. Any other embodiments obtained by those skilled in the art without inventive effort (such as simple transformation of relevant molecular simulation parameters, optimization methods, etc.) are within the scope of protection of this application.

[0045] Furthermore, it should be noted that if any directional indication (such as up, down, left, right, front, back, etc.) is involved in the embodiments of the present invention, the directional indication is only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0046] Furthermore, those skilled in the art should understand that in the actual use of the embodiments of this application, there may be preset thresholds used as the basis for judging the corresponding technical solutions. These thresholds are conventional technical means commonly used in the field to implement functions such as state judgment, condition recognition, and control logic switching. The specific values, setting basis, value selection methods, determination methods, and adjustment rules of the thresholds involved in this technical solution are all conventional technical choices that can be reasonably determined by those skilled in the art based on conventional technical factors such as actual application scenarios, system working states, characteristics of the detection object, hardware performance parameters, and functional requirements, through conventional experiments, calibrations, and debugging. The specific setting and adjustment of the aforementioned thresholds will not cause this technical solution to be unimplementable as a whole, nor will it affect the realization of the core concept and the achievement of the technical effects of this technical solution.

[0047] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, in the embodiments of this invention, "multiple" refers to two or more. Moreover, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A method for constructing a full-atom numerical model of calcium silicate hydrate (CSH), characterized in that, include: Based on molecular dynamics methods, tricalcium silicate / dicalcium silicate molecular models were constructed using the Materials Studio software platform. Using the Amorphous Cell module of the software platform, a CSH prepolymer model was established by randomly stacking water molecules into a tricalcium silicate / dicalcium silicate molecular model based on the Monte Carlo method. The CSH prepolymer model was pre-optimized using the steepest descent method, and the interatomic interactions were described using the Dreiding force field. Density functional theory was used to perform geometric optimization on the molecular configuration involved in the CSH prepolymer model to obtain molecular structure parameters. These molecular structure parameters were used to verify and correct specified parameters in the original Dreiding force field, and the corrected force field was defined as the Dreiding-CSH force field. Then, based on the Dreiding-CSH force field, the CSH prepolymer model was dynamically relaxed to obtain the initial configuration; Based on the initial configuration, a cross-linking program was written using molecular dynamics methods, and a CSH model with a three-dimensional cross-linked structure was constructed by simulating the CSH hydration reaction process. The crosslinking procedure is used to construct a CSH model with a specified degree of crosslinking.

2. The method for constructing a full-atom numerical model of calcium silicate hydrate (CSH) as described in claim 1, characterized in that, The CSH prepolymer model includes water molecules (H2O) and calcium ions (Ca). 2+ Silicon-oxygen tetrahedral SiO4 4- .

3. The method for constructing a full-atom numerical model of calcium silicate hydrate (CSH) as described in claim 1, characterized in that, Based on the CASTEP module of the software platform, density functional theory is used to perform geometric optimization of the silicon-oxygen tetrahedra and water molecules in the CSH prepolymer model. During the geometric optimization process: The exchange correlation energy is approximated using a generalized gradient of the PBE form. The electron-nuclear interaction is described using the OTFG-ultrasoft pseudopotential; The optimization method is based on the LBFGS algorithm; Brillouin zones are sampled using a 4×4×4 k-point grid.

4. The method for constructing a full-atom numerical model of calcium silicate hydrate (CSH) as described in claim 1, characterized in that, The crosslinking program, written in Perl, specifies silicon and oxygen atoms as the primary bonding sites, with silicon atoms serving as the nucleation framework. The crosslinking program executes the following steps: Step 1. Perform cross-linking bonding operation: Set the chemical bond formation to cross-linking of silicon-oxygen tetrahedral single cells into chains, generating silicon-oxygen tetrahedra with different degrees of hydroxylation; Step 2. After cross-linking, the conjugate gradient optimization algorithm is used to perform static optimization on silicon-oxygen tetrahedra with different degrees of hydroxylation, and kinetic relaxation is carried out under the NVT ensemble to provide optimized configurations for subsequent cross-linking. Step 3. Gradually increase the cross-linking radius until a branched CSH intermediate is formed; Step 4. Based on the configuration of the CSH intermediate, reset the silicon / oxygen atom bonding sites and set a setting that allows chain-like CSH to self-crosslink in order to form a network structure model; Step 5. For numerical models that have reached the preset degree of crosslinking, dynamic relaxation is performed under the NPT ensemble to finally complete the construction of a three-dimensional crosslinked structure CSH all-atom numerical model with the specified degree of crosslinking.

5. The method for constructing a full-atom numerical model of calcium silicate hydrate (CSH) as described in claim 1, characterized in that, The CSH all-atom numerical model also verifies the isotropic or anisotropic characteristics exhibited by CSH with different degrees of crosslinking in macroscopic mechanical response based on the analysis of the material's elastic constants. The mechanical property calculation is based on the constant strain method.

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