Nanoscale-based wollastonite carbonization mechanism analysis method

Abstract

The invention discloses an analysis method of a wollastonite carbonization mechanism based on a nano-scale. Relates to a simulation technology for predicting a wollastonite carbonization mechanism by adopting de novo molecular dynamics and meta-dynamics. And a digital research thought is creatively provided for the low-carbon design of the cement-based material. The analysis method comprises the steps of S1, model construction, S2, simulation setting, S3, result analysis and S4, result extraction. According to the method, the reaction free energy surface is disclosed innovatively through meta-dynamics, so that the reaction path is known quantitatively, and a digital research thought is creatively provided for cement-based material design. By researching the adsorption behavior of water molecules, carbon dioxide and carbonic acid molecules on the CS surface and the interaction between the molecules and the surface, the hydration mechanism and the carbonization mechanism are disclosed, which are of great significance for realizing the high-carbonization-performance and high-stability carbon sequestration material and understanding the carbonization behavior of the carbon sequestration material.

Description

Technical Field

[0001] The invention relates to the field of cement in building materials, and in particular to a simulation technology for predicting the carbonization mechanism of wollastonite by using ab initio molecular dynamics and metadynamics. Background Art

[0002] The rapid increase in CO2 concentration has led to global warming and abnormal climate. Today, the high demand for cement as a building material has led to more than 7% of anthropogenic CO2 emissions. Several effective methods have been proposed to reduce CO2 emissions, such as the use of low-carbon clinker and clean energy. Among these measures, mineral carbonation (MC) has attracted widespread attention due to its ability to store CO2 safely and permanently. Wollastonite (CaSiO3, CS) is a candidate material for mineral carbonation (MC) due to its large Gibbs free energy change of carbonation reaction (-41.6 kJ / mol), low Ca / Si ratio and low synthesis temperature. Wollastonite cement cured with mineral carbonation reduces the global warming potential (GWP) by 30.3% compared with ordinary Portland cement cured with steam. However, the carbonation rate of CS under natural conditions is similar to that of tricalcium silicate (C3S) and dicalcium silicate (C2S). So far, some acceleration methods have been considered in experiments to increase the carbonation rate, such as thermal pretreatment, mechanical activation and CO2 curing. However, theoretical research that is beneficial to improving the carbonization rate of CS is still lacking, and the process and influencing factors of CS carbonization activity still rely mainly on relatively limited experimental tests.

[0003] In recent years, increasingly mature atomic simulation technology has been widely used in the complex field of cement chemistry. It has become a technological development trend in this field by exploring the essential relationship between carbonization activity and surface microstructure at the nanoscale to make up for the shortcomings of experimental testing in understanding the microstructure.

[0004] Therefore, faced with the critical situation that existing technologies are difficult to characterize the early carbonization mechanism of wollastonite, how to use atomic simulation technology to reveal the essential relationship between carbonization activity and surface microstructure at the nanoscale, and then provide a basic theoretical basis for optimizing the CS carbonization rate in the field of low-carbon cement preparation, has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of the key situation that it is difficult to characterize the early carbonization mechanism of wollastonite through experiments in the prior art, the present invention provides an analysis method of the carbonization mechanism of wollastonite based on the nanoscale; and pioneers a digital research idea for the low-carbonization design of cement-based materials.

[0006] The present invention provides a method for analyzing the carbonization mechanism of wollastonite based on nanoscale, comprising the following steps:

[0007] S1. Model construction:

[0008] CS surface cross-section model construction, structural optimization of CS surface cross-section model through first principle software, and selection of reasonable structure according to the size of surface energy;

[0009] The construction of hydration simulation models, including the construction of models for hydration simulation and the construction of models for water dissociation simulation;

[0010] Construction of carbonation simulation models, including models for carbonic acid dissociation, calcium dissolution and carbon dioxide activation;

[0011] S2. Simulation settings:

[0012] Settings for structural optimization of CS surface section models;

[0013] The setup of hydration simulations, including ab initio molecular dynamics setup for hydration simulations and metadynamics setup for water dissociation simulations;

[0014] Setup for carbonation simulations, including metadynamic setup for carbonic acid dissociation, calcium dissolution, and carbon dioxide activation simulations;

[0015] S3. Result analysis:

[0016] Analysis of hydration simulations, including ab initio molecular dynamics trajectory analysis of hydration simulations and metadynamic free energy surface analysis of water dissociation simulations;

[0017] Analysis of carbonation simulations, including metadynamic free energy surface analysis of carbonic acid dissociation, calcium dissolution, and carbon dioxide activation simulations;

[0018] S4. Results extraction:

[0019] Based on the analysis of atomic trajectories and free energy surfaces in S3, the early hydration and carbonization routes of CS were obtained.

[0020] Furthermore, the CS surface section model in step S1 includes:

[0021] On the (001) surface of CS, the vacuum layer is 1.5 nm, and a 2×2×1 supercell is established, which is divided into terminals 1, 2, 3, 4, and 5 according to the height of the section.

[0022] On the (100) surface of CS, the vacuum layer is 1.5 nm, and a 2×2×1 supercell is established, which is divided into terminals 6, 7, 8, 9, 10, and 11 according to the height of the section.

[0023] Furthermore, the hydration simulation model is based on the 3rd terminal of the CS (001) surface. A water layer consisting of 60 water molecules is placed at

[0024] The model of water dissociation simulation, after the hydration simulation is performed for 10 ps, ​​the structure of the last frame is selected as the initial structure of the water dissociation model.

[0025] Furthermore, the carbonization simulation model includes:

[0026] The model of carbonic acid dissociation takes the terminal 3 of the CS(001) surface as the base and A water layer consisting of 59 water molecules and one carbonic acid molecule is placed at

[0027] The calcium dissolution model, after the hydration simulation is performed for 10 ps, ​​the structure of the last frame is selected as the initial structure of the calcium dissolution model;

[0028] For the carbon dioxide activated model, after the calcium dissolution model converges, the structure of the last frame is selected, and one of the water molecules is replaced by carbon dioxide as the initial structure of the carbon dioxide activated model.

[0029] Furthermore, in step S2, the CS surface cross-section model is structurally optimized by using simulation software VASP, CP2K and Plumed software package, and the ab initio molecular dynamics and metadynamics simulation methods are as follows:

[0030] a. Settings for CS surface section model structure optimization:

[0031] The CS surface cross-section model is converted into a .vasp format that can be read by VASP, and four input files of the simulation optimization software VASP are set: the calculation control parameter file INCAR, the Brillouin zone K-point sampling setting file, the file describing the system structure, and the pseudopotential file describing the charge distribution. Then, the simulation optimization software VASP is used to perform self-consistent calculations for structural optimization, and the model is optimized for different surface structures. Finally, the stable structure data file after structural optimization is obtained; and the structural stability is judged by comparing the size of the thermodynamic energy surface energy;

[0032] The calculation formula of surface energy is:

[0033]

[0034] Where A is the area of ​​the terminal, is the single point energy of the surface before structure optimization, n is the number of unit cells contained in the surface model, The energy of the surface after the structure is optimized;

[0035] b. Settings for hydration simulation, including:

[0036] The hydration simulation is set up by converting the CS surface cross-section model into a coord.inc file readable by CP2K, setting the input file cp2k.inp of the optimization software CP2K, and then performing ab initio molecular dynamics simulation calculations through the simulation optimization software CP2K, and then performing a hydration molecular dynamics simulation of the surface to obtain the final hydration state of thermodynamic equilibrium;

[0037] The water dissociation simulation is set up by converting the CS surface cross-section model into a coord.inc file readable by CP2K, setting the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and scanning the free energy surface of the water dissociation process with a specific hydrogen-oxygen bond length as a set variable for the water dissociation process;

[0038] c. Carbonization simulation settings, including:

[0039] The setting of carbonic acid dissociation simulation is as follows: the CS surface cross-section model is converted into a coord.inc file readable by CP2K; the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package are set; for the carbonic acid dissociation process, a specific hydrogen-oxygen distance is used as a collective variable to scan the free energy surface of the carbonic acid dissociation process;

[0040] The setting of calcium dissolution simulation is to convert the CS surface cross-section model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and for the calcium dissolution process, use the calcium oxygen coordination number as a collective variable to scan the free energy surface of the calcium dissolution process;

[0041] The setting of carbon dioxide activation simulation is to convert the CS surface cross-section model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and for the carbon dioxide activation process, use the specific carbon-oxygen distance as the collective variable to scan the free energy surface of the carbon dioxide activation process.

[0042] Furthermore, the analysis method of the simulation result in step S2 in step S3 is specifically as follows:

[0043] Ⅰ) Analysis of hydration simulation, including:

[0044] Analysis of hydration simulation: obtaining the pdb trajectory file in the hydration simulation, and performing trajectory, radial distribution function, and root mean square displacement analysis on the file;

[0045] Analysis of water dissociation simulation: Use the Plumed software package to process the hills file obtained in the S2 simulation to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of water dissociation;

[0046] II) Analysis of carbonization simulation

[0047] Analysis of the simulation of carbonic acid dissociation: The hills file obtained by the simulation in S2 was processed using the Plumed software package to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbonic acid dissociation;

[0048] Analysis of calcium dissolution simulation: The hills file obtained by simulation in S2 was processed using the Plumed software package to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of calcium dissolution;

[0049] The analysis of the carbon dioxide activation simulation uses the Plumed software package to process the hills file obtained from the simulation in S2 to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbon dioxide activation.

[0050] Furthermore, the results of the refinement in step S4 are specifically:

[0051] The reaction mechanism of CS early hydration includes:

[0052] The adsorption behavior and migration of water molecules and the interaction between surface atoms and water molecules; the route and mechanism of water dissociation, including direct dissociation and dissociation promoted by proton transfer; and

[0053] The reaction mechanism of early carbonization of CS includes:

[0054] The dissociation route and mechanism of carbonic acid molecules on the CS surface, including direct dissociation and dissociation promoted by proton transfer; the reaction route and mechanism of calcium dissolution, including dissolution under pure water conditions and dissolution involving carbonic acid molecules; the activation route and mechanism of carbon dioxide.

[0055] The analytical method of the present invention innovatively reveals the reaction free energy surface through metadynamics, thereby quantitatively understanding the reaction path, and pioneering a digital research idea for cement-based material design. By studying the adsorption behavior of water molecules, carbon dioxide and carbonic acid molecules on the CS surface and the interaction between molecules and the surface, its hydration mechanism and carbonization mechanism are revealed, which is of great significance for realizing high carbonization performance and high stability carbon sequestration materials and understanding their carbonization behavior. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a flow chart of the prediction method of the present invention,

[0057] Figure 2 is a technical route flow chart for implementing the prediction method of the present invention,

[0058] Figure 3 is the CS(001) surface model,

[0059] Figure 4 This is a schematic diagram of the hydration simulation model of the CS(001) surface.

[0060] Figure 5 This is a schematic diagram of the water dissociation simulation model on the CS(001) surface.

[0061] Figure 6 This is a schematic diagram of the simulation model of carbonic acid dissociation on the CS(001) surface.

[0062] Figure 7 This is a schematic diagram of the simulation model of calcium dissolution on the CS(001) surface.

[0063] Figure 8 This is a schematic diagram of the simulation model of carbon dioxide activation on the CS(001) surface.

[0064] Fig. 9 is the trajectory of the interfacial oxygen atoms in the hydration simulation,

[0065] Fig.10 is the radial distribution function of each atomic pair on the interface in the hydration simulation,

[0066] Fig.11 is the root mean square displacement of each atom on the interface in the hydration simulation,

[0067] Fig.12 It is the reaction route and energy change of water dissociation simulation.

[0068] Fig.13 It is the reaction route and energy change of carbonic acid dissociation simulation.

[0069] Fig.14 It is the reaction route and energy change of calcium dissolution simulation.

[0070] Fig.15 It is the reaction route and capacity change of carbon dioxide activation. DETAILED DESCRIPTION

[0071] In order to make the application purpose, technical solution and beneficial technical effect of the present application clearer, the present application is further described in detail in conjunction with the embodiments below. It should be understood that the embodiments described in this specification are only for explaining the present application, not for limiting the present application.

[0072] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range, and any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0073] In the description of the present application, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number, and the “multiple” in “one or more” means two or more than two.

[0074] The above application content of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0075] like Figure 1 , 2 As shown, the present invention is based on a nanoscale carbonization mechanism analysis method of wollastonite, and the prediction of the carbonization mechanism of low-carbon cementitious material CS is regulated by a wet carbonization mechanism. The method comprises the following steps:

[0076] S1. Model construction,

[0077] 1. Surface model construction:

[0078] Build a reasonable CS surface cross-section (slab) model, optimize the slab structure using first-principles software, and select the most reasonable structure based on the size of the surface energy;

[0079] The (001) surface (crystal plane) of CS, the vacuum layer is Create a 2×2×1 supercell and divide it into terminals 1, 2, 3, 4, and 5 according to the height of the section.

[0080] The (100) surface of CS has a vacuum layer of Create a 2×2×1 supercell and divide it into terminals 6, 7, 8, 9, 10, and 11 according to the height of the section.

[0081] In this embodiment, there are 11 terminals on the (100) and (001) surface models of CS, see Figure 3 , by comparing the surface energy, we can judge the surface stability, see Table 1:

[0082] Table 1: Surface energy of CS surface models with different terminals

[0083] serial number Surface energy (J / m2) 1 3.04 2 1.94 3 1.06 4 1.89 5 1.10 6 1.81 7 1.19 8 2.14 9 3.37 10 2.17 11 1.37

[0084] Depend on Figure 3 and Table 1, terminal 3 of the CS(001) surface is selected as the model.

[0085] 2. Construction of hydration simulation model:

[0086] Model construction for hydration simulation, see Figure 4 . With the 3rd terminal of the CS(001) surface as the base, A water layer consisting of 60 water molecules is placed at

[0087] Model for water dissociation simulation, see Figure 5 After the above hydration simulation was performed for 10 ps, ​​the structure of the last frame was selected as the initial structure of the water dissociation model.

[0088] Furthermore, the carbonization simulation model is constructed:

[0089] Model of carbonic acid dissociation, see Figure 6 The 3rd terminal of the CS(001) surface is used as the base. A water layer consisting of 59 water molecules and one carbonic acid molecule is placed at

[0090] For models of calcium dissolution, see Figure 7 After the above hydration simulation was performed for 10 ps, ​​the structure of the last frame was selected as the initial structure of the calcium dissolution model.

[0091] Model of carbon dioxide activation, see Figure 8 After the above calcium dissolution model converges, the structure of its last frame is selected, and one of the water molecules is replaced by carbon dioxide as the initial structure of the carbon dioxide activation model.

[0092] S2. Simulation settings

[0093] The first-principles calculation software VASP was used to optimize the structures of different terminal surfaces, and the terminals were selected according to the surface energy. The molecular dynamics software CP2K and the Plumed software package were used to simulate the hydration process. The molecular dynamics software CP2K and the Plumed software package were used to simulate the carbonization process.

[0094] a. The method for structural optimization of different terminal surfaces using the first principle calculation software VASP is as follows:

[0095] The CS structural models of the above-mentioned different surface terminals are converted into .vasp format readable by VASP, and four input files of the simulation optimization software VASP are set: calculation control parameter file INCAR, Brillouin zone K-point sampling setting file, system structure description file and pseudopotential file describing charge distribution. Then, the simulation optimization software VASP is used to perform self-consistent calculation of structural optimization, and the model is optimized for different surface structures, and finally the stable structure data file after structural optimization is obtained; and the structural stability is judged by comparing the size of the thermodynamic energy surface energy;

[0096] The calculation formula of surface energy is:

[0097]

[0098] Where A is the area of ​​the terminal, is the single point energy of the surface before structure optimization, n is the number of unit cells contained in the surface model, The energy of the surface after the structure is optimized;

[0099] b. Methods for simulating the hydration process using molecular dynamics software CP2K and Plumed software package include:

[0100] The simulation method of hydration is to convert the model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K, and then perform ab initio molecular dynamics simulation calculations through the simulation optimization software CP2K to perform hydration molecular dynamics simulation on the CS surface. The simulation step size is set to 0.5fs, the number of steps is set to 20000 steps, and the simulated temperature is 298.15℃.

[0101] The simulation method of water dissociation is to convert the model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and then perform metadynamic simulation through the simulation optimization software CP2K and Plumed. The step size of CP2K is set to 0.5fs, the simulation temperature is 298.15K, and the simulation time is the time for energy convergence. In the Plumed software package, a mild metadynamic method is selected, and the distance between the base oxygen (Os) and the hydrogen (H) in water is set to d1, and the distance between the oxygen in water (Ow) and the hydrogen in water (Hw) is set to d2, and d1-d2 is used as the collective variable one (CV1). A Gaussian peak of 2.5kJ / mol is added to the system every 30 steps, and the bias factor of the system is set to 20.

[0102] c. The method of simulating the carbonization process by using the molecular dynamics software CP2K and the Plumed software package includes:

[0103] The method of carbonic acid dissociation simulation is to convert the model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and then perform metadynamic simulation through the simulation optimization software CP2K and Plumed. The step size of CP2K is set to 0.5fs, the simulation temperature is 298.15K, and the simulation time is the time for energy convergence. In the Plumed software package, a mild metadynamic method is selected, and the distance between oxygen (Oc) in carbonic acid and hydrogen (Hc) in carbonic acid is set to d1, and the distance between hydrogen (Hc) in carbonic acid and hydrogen (Ow) in water is set to d2, with d1-d2 as CV1; the distance between oxygen (Ow) in water and hydrogen (Hw) in water is set to d1, and the distance between substrate oxygen (Os) and hydrogen (Hw) in water is set to d2, with d1-d2 as CV2. A Gaussian peak of 2.5 kJ / mol was added to the system every 30 steps, and the bias factor of the system was set to 20.

[0104] The setting of calcium dissolution simulation, convert the model in S1 into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package. The step size of CP2K is set to 1fs, the simulation temperature is 298.15K, the simulation time is the time of energy convergence, and the hydrogen atoms are replaced by deuterium atoms. Select the mild metadynamics method in the Plumed software package, set the coordination number of calcium (Ca) and oxygen in water (Ow) to CV1, and the coordination number of calcium (Ca) and substrate oxygen (Os) to CV2. Add a 2.5kJ / mol Gaussian peak to the system every 30 steps, and set the biasfactor of the system to 20.

[0105] The settings for the carbon dioxide activation simulation are as follows: convert the model in S1 into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package. The step size of CP2K is set to 0.5fs, the simulation temperature is 298.15K, and the simulation time is the time for energy convergence. Select the mild metadynamics method in the Plumed software package, and set the distance between the carbon atom (C) of carbon dioxide and the oxygen atom (O) of the active hydroxyl group in water to CV1. Add a 2.5kJ / mol Gaussian peak to the system every 30 steps, and set the biasfactor of the system to 20.

[0106] S3. Result Analysis

[0107] Ⅰ) Analysis of hydration simulation, including:

[0108] Analysis of hydration simulation, obtain the pdb trajectory file in the hydration simulation, and perform trajectory analysis on the file ( Fig. 9 ), radial distribution function ( Fig.10 ), RMS displacement analysis ( Fig.11 ). Fig. 9 It shows that the interfacial water molecules are mainly distributed on the bridge sites of calcium atoms, mainly by molecular adsorption. Fig.10 This indicates that a stable water layer is formed on the interface during hydration, and the interaction between calcium and substrate oxygen is weakened. The main interaction between substrate oxygen and hydrogen atoms is hydrogen bonding, so the adsorption of water molecules on the surface is mainly molecular adsorption. Fig.11 It shows that the activity of surface atoms is ranked as Ca, Si, and O.

[0109] For the analysis of water dissociation simulation, the hills file obtained by simulation in S2 was processed using the Plumed software package to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of water dissociation. Fig.12 This indicates that proton transfer reduces the energy barrier for water dissociation.

[0110] II) Analysis of carbonization simulation

[0111] The analysis of the carbonic acid dissociation simulation used the Plumed software package to process the hills file obtained from the simulation in S2 to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbonic acid dissociation. Fig.13 It shows that proton transfer reduces the dissociation energy barrier of carbonic acid, and the most stable form of carbon species is bicarbonate.

[0112] The analysis of calcium dissolution simulation uses the Plumed software package to process the hills file obtained from the simulation in S2 to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of calcium dissolution. Fig.14 It shows that in the early stage of calcium dissolution, carbonic acid significantly reduces the energy barrier of calcium dissolution and promotes calcium dissolution; in the later stage of calcium dissolution, carbonic acid changes the dissolution kinetics of calcium.

[0113] The analysis of the carbon dioxide activation simulation uses the Plumed software package to process the hills file obtained from the simulation in S2 to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbon dioxide activation. Fig.15 It shows that due to proton exchange, active hydroxyl groups appear in the solution after calcium dissolution. The active hydroxyl groups have strong electron-donating ability and can activate carbon dioxide.

[0114] S4. Draw conclusions

[0115] Reaction mechanism of early hydration of CS:

[0116] Water molecules are mainly adsorbed on the (001) surface of CS in the form of molecular adsorption, and proton transfer promotes the dissociative adsorption of water molecules.

[0117] The reaction mechanism of early carbonization of CS includes:

[0118] Proton transfer promotes the dissociation of carbonate molecules, which mainly exist on the surface of CS(001) in the form of bicarbonate. Carbonate molecules promote the dissolution of calcium ions and change the dissolution kinetics. The active hydroxyl groups produced by calcium dissolution can further activate carbon dioxide.

[0119] Through the above technical measures, after simulation, the key physical and chemical processes of hydration and carbonization are mastered, such as molecular dissociation, proton transfer, calcium dissolution, etc. In this way, those skilled in the art can improve the kinetics of these key processes by designing the structure of wollastonite, such as doping or defect manufacturing, or regulating the carbonization solution environment, thereby achieving the enhancement of wollastonite carbonization reaction and high-performance wollastonite carbon sequestration materials.

[0120] The calculation parameters involved in this method are as follows: All simulations were performed using VASP and CP2K calculation programs. VASP geometry optimization parameters: The generalized gradient approximation functional (GGA) was used to approximate the exchange-correlation potential, and the four crystal models were continuously optimized until the energy difference and force difference were less than 1×10-5eV / atom and The cutoff energy is 500 eV, and 2×2×1 gamma points are used for sampling. The atomic pseudopotentials described by the projected augmented plane wave (PAW) method are O2s22p4, Si3s23p2, Ca3s23p64s2, and H1s1. In addition, DFT-D3 dispersion correction is selected to consider van der Waals correction (VDW). CP2K dynamic parameters: The water layer is generated using the PACKMOL code. PBE functions and DFT-D3 corrections are used in the simulation, and the reciprocal space is sampled using gamma points. The core electrons are described by the Goedecker-Teter-Hutter (GTH) pseudopotential, and the valence electron density is established on the double Zeta valence polarization (DZVP-MOLOPT-SR-GTH) basis set and the auxiliary plane wave basis set with a cutoff energy of 500 Ry. The convergence criteria for energy and self-consistent field are set to 10-10 and 10-5 Hartree, respectively.

[0121] The present invention firstly selects the most reasonable surface model according to the size of the surface energy, and builds different models for hydration and carbonization reactions based on the model.

[0122] Secondly, for the hydration and carbonization reactions, the parameters of the ab initio molecular dynamics simulation software CP2K and the metadynamics Plumed software package were set.

[0123] Secondly: analyze the trajectory, radial distribution function and root mean square displacement of the pdb trajectory file obtained from the ab initio molecular dynamics simulation; analyze the free energy surface of the hills file obtained from the metadynamics simulation.

[0124] Finally, based on the analysis results, the early reaction mechanisms and routes of hydration and carbonization are summarized.

[0125] This invention innovatively reveals the reaction free energy surface through metadynamics, thereby quantitatively understanding the reaction path, and pioneering a digital research idea for cement-based material design. By studying the adsorption behavior of water molecules, carbon dioxide and carbonic acid molecules on the CS surface and the interaction between molecules and the surface, the carbonization mechanism of wollastonite is analyzed from the nanoscale, revealing its hydration mechanism and carbonization mechanism, which is of great significance for realizing high carbonization performance and high stability carbon sequestration materials and understanding their carbonization behavior.

[0126] It should be noted that the above specific implementations are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art should understand that various modifications, equivalent substitutions, changes, etc. can be made to the present invention based on the technical content disclosed in this application document. However, as long as these changes do not deviate from the spirit of the present invention, they should be within the scope of protection of the present invention. In addition, some terms used in the specification and claims of this application are not restrictive, but are only for the convenience of description.

Claims

1. A method for analyzing the carbonization mechanism of wollastonite based on nanoscale, characterized in that: The following steps are involved: S1. Model construction: CS surface cross-section model construction, structural optimization of CS surface cross-section model through first principle software, and selection of reasonable structure according to the size of surface energy; The construction of hydration simulation models, including the construction of models for hydration simulation and the construction of models for water dissociation simulation; Construction of carbonation simulation models, including models for carbonic acid dissociation, calcium dissolution and carbon dioxide activation; S2. Simulation settings: Settings for structural optimization of CS surface section models; The setup of hydration simulations, including ab initio molecular dynamics setup for hydration simulations and metadynamics setup for water dissociation simulations; Setup for carbonation simulations, including metadynamic setup for carbonic acid dissociation, calcium dissolution, and carbon dioxide activation simulations; S3. Result analysis: Analysis of hydration simulations, including ab initio molecular dynamics trajectory analysis of hydration simulations and metadynamic free energy surface analysis of water dissociation simulations; Analysis of carbonation simulations, including metadynamic free energy surface analysis of carbonic acid dissociation, calcium dissolution, and carbon dioxide activation simulations; S4. Results extraction: Based on the analysis of atomic trajectories and free energy surfaces in S3, the early hydration and carbonization routes of CS were obtained.

2. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: The CS surface section model in step S1 includes: On the (001) surface of CS, the vacuum layer is 1.5 nm, and a 2×2×1 supercell is established, which is divided into terminals 1, 2, 3, 4, and 5 according to the height of the section. On the (100) surface of CS, the vacuum layer is 1.5 nm, and a 2×2×1 supercell is established, which is divided into terminals 6, 7, 8, 9, 10, and 11 according to the height of the section.

3. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 2, characterized in that: The hydration simulation model is based on the 3rd terminal of the CS (001) surface. A water layer consisting of 60 water molecules is placed at The model of water dissociation simulation, after the hydration simulation is performed for 10 ps, ​​the structure of the last frame is selected as the initial structure of the water dissociation model.

4. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 2, characterized in that: The carbonization simulation model includes: The model of carbonic acid dissociation takes the terminal 3 of the CS(001) surface as the base and A water layer consisting of 59 water molecules and one carbonic acid molecule is placed at The calcium dissolution model, after the hydration simulation is performed for 10 ps, ​​the structure of the last frame is selected as the initial structure of the calcium dissolution model; For the carbon dioxide activated model, after the calcium dissolution model converges, the structure of the last frame is selected, and one of the water molecules is replaced by carbon dioxide as the initial structure of the carbon dioxide activated model.

5. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: In step S2, the CS surface cross-section model is structurally optimized by using simulation software VASP, CP2K and Plumed software package, and the ab initio molecular dynamics and metadynamics simulation methods are as follows: a. Settings for CS surface section model structure optimization: The CS surface cross-section model is converted into a .vasp format that can be read by VASP, and four input files of the simulation optimization software VASP are set: the calculation control parameter file INCAR, the Brillouin zone K-point sampling setting file, the file describing the system structure, and the pseudopotential file describing the charge distribution. Then, the simulation optimization software VASP is used to perform self-consistent calculations for structural optimization, and the model is optimized for different surface structures. Finally, the stable structure data file after structural optimization is obtained; and the structural stability is judged by comparing the size of the thermodynamic energy surface energy; The calculation formula of surface energy is: Where A is the area of ​​the terminal, is the single point energy of the surface before structure optimization, n is the number of unit cells contained in the surface model, The energy of the surface after the structure is optimized; b. Settings for hydration simulation, including: The hydration simulation is set up by converting the CS surface cross-section model into a coord.inc file readable by CP2K, setting the input file cp2k.inp of the optimization software CP2K, and then performing ab initio molecular dynamics simulation calculations through the simulation optimization software CP2K, and then performing a hydration molecular dynamics simulation of the surface to obtain the final hydration state of thermodynamic equilibrium; The water dissociation simulation is set up by converting the CS surface cross-section model into a coord.inc file readable by CP2K, setting the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and scanning the free energy surface of the water dissociation process with a specific hydrogen-oxygen bond length as a set variable for the water dissociation process; c. Carbonization simulation settings, including: The setting of carbonic acid dissociation simulation is as follows: the CS surface cross-section model is converted into a coord.inc file readable by CP2K; the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package are set; for the carbonic acid dissociation process, a specific hydrogen-oxygen distance is used as a collective variable to scan the free energy surface of the carbonic acid dissociation process; The setting of calcium dissolution simulation is to convert the CS surface cross-section model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and for the calcium dissolution process, use the calcium oxygen coordination number as a collective variable to scan the free energy surface of the calcium dissolution process; The setting of carbon dioxide activation simulation is to convert the CS surface cross-section model into a coord.inc file readable by CP2K, set the input file cp2k.inp of the optimization software CP2K and the input file plumed.dat of the Plumed software package, and for the carbon dioxide activation process, use the specific carbon-oxygen distance as the collective variable to scan the free energy surface of the carbon dioxide activation process.

6. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: The specific analysis method of step S3 for the simulation results in step S2 is: Ⅰ) Analysis of hydration simulation, including: Analysis of hydration simulation: obtaining the pdb trajectory file in the hydration simulation, and performing trajectory, radial distribution function, and root mean square displacement analysis on the file; Analysis of water dissociation simulation: Use the Plumed software package to process the hills file obtained in the S2 simulation to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of water dissociation; II) Analysis of carbonization simulation Analysis of the simulation of carbonic acid dissociation: The hills file obtained by the simulation in S2 was processed using the Plumed software package to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbonic acid dissociation; Analysis of calcium dissolution simulation: The hills file obtained by simulation in S2 was processed using the Plumed software package to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of calcium dissolution; The analysis of the carbon dioxide activation simulation uses the Plumed software package to process the hills file obtained from the simulation in S2 to obtain the free energy surface of the reaction, record the local energy minima on the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction route of carbon dioxide activation.

7. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: The results of step S4 extraction are as follows: The reaction mechanism of CS early hydration includes: The adsorption behavior and migration of water molecules and the interaction between surface atoms and water molecules; the route and mechanism of water dissociation, including direct dissociation and dissociation promoted by proton transfer; and The reaction mechanism of early carbonization of CS includes: The dissociation route and mechanism of carbonic acid molecules on the CS surface, including direct dissociation and dissociation promoted by proton transfer; the reaction route and mechanism of calcium dissolution, including dissolution under pure water conditions and dissolution involving carbonic acid molecules; the activation route and mechanism of carbon dioxide.

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