An analysis method based on nanoscale wollastonite carbonization mechanism

Abstract

The application discloses an analysis method based on a nanometer scale wollastonite carbonization mechanism, and relates to a simulation technology for predicting the wollastonite carbonization mechanism by using ab initio molecular dynamics and metadynamics. The application discloses an analysis method based on a nanometer scale wollastonite carbonization mechanism, and relates to a simulation technology for predicting the wollastonite carbonization mechanism by using ab initio molecular dynamics and metadynamics. The application discloses an analysis method based on a nanometer scale wollastonite carbonization mechanism, and relates to a simulation technology for predicting the wollastonite carbonization mechanism by using ab initio molecular dynamics and metadynamics. The application discloses an analysis method based on a nanometer scale wollastonite carbonization mechanism, and relates to a simulation technology for predicting the wollastonite carbonization mechanism by using ab initio molecular dynamics and metadynamics. The application discloses an analysis method based on a nanometer scale wollastonite carbonization mechanism, and relates to a simulation technology for predicting the wollastonite carbonization mechanism by using ab initio molecular dynamics and metadynamics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cement in building materials, and particularly relates to a simulation technology for predicting carbonation mechanism of wollastonite by ab initio molecular dynamics and metadynamics. BACKGROUND

[0002] The rapid growth of carbon dioxide concentration leads to global warming and abnormal climate. Nowadays, the high demand of cement as building materials leads to more than 7% of anthropogenic carbon dioxide emissions. Some effective methods have been proposed to reduce carbon dioxide emissions, such as using low-carbon clinker and clean energy. Among these measures, mineral carbonation (MC) has attracted extensive attention due to its safe and permanent storage of carbon dioxide. Wollastonite (CaSiO3, CS) has become a candidate material for mineral carbonation (MC) due to its large Gibbs free energy change (-41.6 kJ / mol) of carbonation reaction, low Ca / Si ratio and low synthesis temperature. Compared with ordinary Portland cement using steam curing, wollastonite Portland cement using mineral carbonation curing reduces the global warming potential (GWP) by 30.3%. 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 improve the carbonation rate, such as thermal pretreatment, mechanical activation and carbon dioxide curing. However, there is still a lack of theoretical research on the carbonation rate of CS. The process and influencing factors of CS carbonation activity still mainly depend on limited experimental tests.

[0003] In recent years, the increasingly mature atomic simulation technology has been widely applied in the field of complex cement chemistry, which explores the essential relationship between carbonation activity and surface microstructure at the nanoscale to make up for the lack of experimental tests in microstructure understanding, and becomes the development trend of the field.

[0004] Therefore, in the face of the key status quo that the existing technology is difficult to characterize the early carbonation mechanism of wollastonite, how to use atomic simulation technology to reveal the essential relationship between carbonation activity and surface microstructure at the nanoscale, and then provide a theoretical basis for optimizing the carbonation rate of CS in the field of low-carbon cement preparation, has become a technical problem to be solved in the field. SUMMARY

[0005] The present application provides an analysis method of carbonation mechanism of wollastonite based on nanoscale, aiming at the key status quo that the existing technology is difficult to characterize the early carbonation mechanism of wollastonite through experiments, and provides an innovative idea of digital research for low-carbon design of cement-based materials.

[0006] The analysis method of carbonation mechanism of wollastonite based on nanoscale provided by the present application comprises the following steps:

[0007] S1, model construction:

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

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

[0010] carbonation simulation model construction, including the construction of the model for carbonic acid dissociation, calcium dissolution and carbon dioxide activation;

[0011] S2, simulation setting:

[0012] Setting of CS surface cross-section model structure optimization;

[0013] Setting of hydration simulation, including ab initio molecular dynamics setting of hydration simulation and metadynamics setting of water dissociation simulation;

[0014] Setting of carbonation simulation, including metadynamics setting of carbonic acid dissociation, calcium dissolution and carbon dioxide activation simulation;

[0015] S3, result analysis:

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

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

[0018] S4, achievement refinement:

[0019] According to the analysis of atomic trajectory and free energy surface in S3, the early hydration and carbonation route of CS is obtained.

[0020] Further, the CS surface cross-section model in step S1 comprises:

[0021] The (001) surface of CS, the vacuum layer is 1.5nm, the supercell of 2x2x1 is established, and the terminal is divided into 1, 2, 3, 4, 5 according to the height of the section.

[0022] The (100) surface of CS, the vacuum layer is 1.5nm, the supercell of 2x2x1 is established, and the terminal is divided into 6, 7, 8, 9, 10, 11 according to the height of the section.

[0023] Further, the water hydration simulation model is based on the No. 3 terminal of the CS (001) surface, a water layer composed of 60 water molecules is placed at a distance of 3 Å from the end surface, and the vacuum layer thickness is 20 Å;

[0024] The water dissociation simulation model is based on the last frame structure after the water hydration simulation is performed for 10 ps.

[0025] Further, the carbonation simulation model comprises:

[0026] The carbonic acid dissociation model is based on the No. 3 terminal of the CS (001) surface, a water layer composed of 59 water molecules and one carbonic acid molecule is placed at a distance of 3 Å from the end surface, and the vacuum layer thickness is 20 Å;

[0027] The calcium dissolution model is based on the last frame structure after the water hydration simulation is performed for 10 ps.

[0028] The carbon dioxide activation model is based on the last frame structure after the calcium dissolution model converges, and one water molecule is replaced by carbon dioxide as the initial structure of the carbon dioxide activation model.

[0029] Further, the step S2 is performed by simulating software VASP, CP2K and Plumed software package, and the methods of ab initio molecular dynamics and metadynamics simulation are:

[0030] a. Setting of the structure optimization of the CS surface section model:

[0031] The CS surface section model is converted into a.vasp format readable by VASP, four input files of the simulation optimization software VASP are set, including a calculation control parameter file INCAR, a Brillouin zone K point sampling setting file, a system structure file and a pseudopotential file describing the charge distribution, and then the structure optimization self-consistent calculation is performed by the simulation optimization software VASP, the model optimization is performed for different surface structures, and finally the stable structure data file after the structure optimization is obtained; and the structure stability is judged by comparing the size of the thermodynamic energy surface energy;

[0032] The calculation formula of the surface energy is:

[0033]

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

[0035] b、hydration simulation settings, including:

[0036] hydration simulation settings, 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 calculation by the simulation optimization software CP2K, and then performing hydration molecular dynamics simulation on the surface to obtain the thermodynamic equilibrium hydration end state;

[0037] Hydrolysis simulation settings, 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 for the hydrolysis process, a specific hydrogen-oxygen bond length is used as a collective variable to scan the free energy surface of the hydrolysis process.

[0038] c、carbonation simulation settings, including:

[0039] Carbonate dissociation simulation settings, 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 for the carbonate dissociation process, a specific hydrogen-oxygen distance is used as a collective variable to scan the free energy surface of the carbonate dissociation process.

[0040] Calcium dissolution simulation settings, 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 for the calcium dissolution process, the calcium-oxygen coordination number is used as a collective variable to scan the free energy surface of the calcium dissolution process.

[0041] Carbon dioxide activation simulation settings, 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 for the carbon dioxide activation process, a specific carbon-oxygen distance is used as a collective variable to scan the free energy surface of the carbon dioxide activation process.

[0042] Further, the analysis method of the simulation results in step S2 is specifically:

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

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

[0045] Analysis of the hydrolysis simulation, the hills file obtained in S2 is processed by Plumed software package to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, and finally obtain the reaction route of the hydrolysis;

[0046] Ⅱ)、Carbonization simulation analysis

[0047] Analysis of the carbonic acid dissociation simulation, the hills file obtained in S2 is processed by Plumed software package to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, and finally obtain the reaction route of the carbonic acid dissociation;

[0048] Analysis of the calcium dissolution simulation, the hills file obtained in S2 is processed by Plumed software package to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, and finally obtain the reaction route of the calcium dissolution;

[0049] Analysis of the carbon dioxide activation simulation, the hills file obtained in S2 is processed by Plumed software package to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, and finally obtain the reaction route of the carbon dioxide activation.

[0050] Further, the results refined in step S4 are specifically:

[0051] The reaction mechanism of the early hydration of CS, including:

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

[0053] The reaction mechanism of the early carbonization of CS, including:

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

[0055] The analysis method of the application innovatively reveals the reaction free energy surface through metadynamics, so as to quantitatively understand the reaction path, and to provide an innovative digital research idea for cement-based material design. By studying the adsorption behavior of water molecules and carbon dioxide and carbonic acid molecules on the CS surface and the interaction between the molecules and the surface, the hydration mechanism and carbonation mechanism are revealed, which is of great significance for realizing high carbonation performance and high stability carbon storage materials and understanding the carbonation behavior. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a flowchart of the prediction method of the application,

[0057] Figure 2 is a technical route flowchart for implementing the prediction method of the application,

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

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

[0060] Figure 5 is a hydrolysis simulation model schematic diagram of the CS (001) surface,

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

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

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

[0064] Figure 9 is the trajectory of the interface oxygen atom in the hydration simulation,

[0065] Figure 10 is the radial distribution function of each atom pair in the interface in the hydration simulation,

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

[0067] Figure 12 is the reaction route and energy change of the hydrolysis simulation,

[0068] Figure 13 is the reaction route and energy change of the carbonic acid dissociation simulation,

[0069] Figure 14 is the reaction route and energy change of the calcium dissolution simulation,

[0070] Figure 15 is a carbon dioxide activated reaction route and capacity change. DETAILED DESCRIPTION

[0071] In order to make the application purpose, technical scheme and beneficial technical effects of the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the embodiments described in the present specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0072] For the sake of simplicity, only some numerical ranges are explicitly disclosed in the present application. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit be combined with any other upper limit to form a range not explicitly recited. Moreover, although a range of endpoints is recited, each point or individual number within the range is also included in the range. Thus, each point or individual number can be combined as its own lower or upper limit with any other point or individual number or with other lower or upper limits to form a range not explicitly recited.

[0073] In the description of the present application, it should be noted that, unless otherwise specified, "above", "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is two and 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 illustrates the exemplary embodiments more specifically. In many places throughout the application, guidance is provided by a series of embodiments, which can be used in various combinations. In each instance, the enumeration is only representative of a group, and should not be interpreted as exhaustive.

[0075] As shown in Figure 1 , 2 The analysis method of the wollastonite carbonation mechanism based on nanoscale of the present application, through the prediction of the carbonation mechanism of the low-carbon cementitious material CS by the wet carbonation mechanism regulation, comprises the following steps:

[0076] S1, model building,

[0077] 1. Surface model building:

[0078] A reasonable CS surface slab model is built, the slab is structurally optimized by first principle software, and the most reasonable structure is selected according to the size of surface energy;

[0079] The (001) surface (crystal face) of CS, the vacuum layer is 15Å, the supercell of 2×2×1 is established, and the height of the section is divided into 1, 2, 3, 4 and 5 terminals.

[0080] The (100) surface of CS, the vacuum layer is 15 Å, and a 2x2x1 supercell is established, which is divided into 6, 7, 8, 9, 10, and 11 terminals according to the height of the section.

[0081] In this embodiment, there are 11 terminals on the (100) and (001) surface models of CS, as shown in Figure 3 The surface stability is determined by comparing the surface energy, as shown in Table 1:

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

[0083] 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] According to Figure 3 and Table 1, the No. 3 terminal of the CS (001) surface is selected as the model.

[0085] 2. Hydration simulation model building:

[0086] The model building of hydration simulation is shown in Figure 4 The No. 3 terminal of the CS (001) surface is used as the substrate, and a water layer composed of 60 water molecules is placed at a distance of 3 Å from the end surface, and the vacuum layer thickness is 20 Å.

[0087] The model of water dissociation simulation is shown in Figure 5 After the above hydration simulation is performed for 10 ps, the structure of the last frame is selected as the initial structure of the water dissociation model.

[0088] Further, the carbonization simulation model is built:

[0089] The model of carbonic acid dissociation is shown in Figure 6 The No. 3 terminal of the CS (001) surface is used as the substrate, and a water layer composed of 59 water molecules and one carbonic acid molecule is placed at a distance of 3 Å from the end surface, and the vacuum layer thickness is 20 Å.

[0090] The model of calcium dissolution is shown in Figure 7 After the above hydration simulation is performed for 10 ps, the structure of the last frame is selected as the initial structure of the calcium dissolution model.

[0091] The model of carbon dioxide activation is shown in Figure 8 After the above calcium dissolution model converges, the structure of the last frame is selected, and one water molecule is replaced by carbon dioxide as the initial structure of the carbon dioxide activation model.

[0092] S2, simulation setting

[0093] The first principle calculation software VASP is used for structure optimization of different terminal surfaces, and the terminal is selected according to the surface energy; the molecular dynamics software CP2K and the Plumed software package are used for simulating the hydration process; the molecular dynamics software CP2K and the Plumed software package are used for simulating the carbonization process.

[0094] a. The method for structure optimization of different terminal surfaces by the first principle calculation software VASP is:

[0095] The CS structure model of the above different surface terminals is converted into the.vasp format readable by VASP, four input files of the simulation optimization software VASP are set, including the calculation control parameter file INCAR, the Brillouin zone K point sampling setting file, the system structure file and the pseudo-potential file describing the charge distribution, then the structure optimization self-consistent calculation is carried out by the simulation optimization software VASP, the model optimization is carried out for different surface structures, and finally the stable structure data file after structure optimization is obtained; and the structure stability is judged by comparing the size of the thermodynamic energy surface energy;

[0096] The calculation formula of the surface energy is:

[0097]

[0098] Wherein 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, is the energy of the surface after structure optimization;

[0099] b. The method for simulating the hydration process by the molecular dynamics software CP2K and the Plumed software package comprises:

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

[0101] The simulation method of hydrolysis, the model is converted into the 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, and then the metadynamics simulation is carried out by the optimization software CP2K and Plumed. The step length of CP2K is set to 0.5 fs, the simulation temperature is 298.15 K, and the simulation time is the time of energy convergence. In the Plumed software package, a mild metadynamics method is selected, the distance between the base oxygen (Os) and the hydrogen (H) in water is set as d1, the distance between the oxygen (Ow) in water and the hydrogen (Hw) in water is set as d2, and d1-d2 is set as the collective variable (CV1). A Gaussian peak of 2.5 kJ / mol is added to the system every 30 steps, and the biasfactor of the system is set to 20.

[0102] c. The method for simulating the carbonation process by the molecular dynamics software CP2K and the Plumed software package comprises:

[0103] The simulation method of carbonic acid dissociation, the model is converted into the 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, and then the metadynamics simulation is carried out by the optimization software CP2K and Plumed. The step length of CP2K is set to 0.5 fs, the simulation temperature is 298.15 K, and the simulation time is the time of energy convergence. In the Plumed software package, a mild metadynamics method is selected, the distance between the oxygen (Oc) in carbonic acid and the hydrogen (Hc) in carbonic acid is set as d1, the distance between the hydrogen (Hc) in carbonic acid and the hydrogen (Ow) in water is set as d2, and d1-d2 is set as CV1; the distance between the oxygen (Ow) in water and the hydrogen (Hw) in water is set as d1, the distance between the base oxygen (Os) and the hydrogen (Hw) in water is set as d2, and d1-d2 is set as CV2. A Gaussian peak of 2.5 kJ / mol is added to the system every 30 steps, and the biasfactor of the system is set to 20.

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

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

[0106] S3, result analysis

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

[0108] Analysis of hydration simulation, obtain the pdb trajectory file in hydration simulation, and perform trajectory analysis ( Figure 9 ), radial distribution function ( Figure 10 ), and root mean square displacement analysis ( Figure 11 ) on the file. Figure 9 It is shown that the interface water molecules are mainly distributed on the bridge site of calcium atom, and molecular adsorption is dominant. Figure 10 It is shown 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 atom is hydrogen bond interaction, so the adsorption of water molecules on the surface is mainly molecular adsorption. Figure 11 It is shown that the activity of surface atoms is ranked as Ca, Si, and O.

[0109] Analysis of hydrolysis simulation, use Plumed software package to process the hills file obtained in S2 simulation, to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, and finally obtain the reaction route of hydrolysis.Figure 12 It is shown that proton transfer reduces the energy barrier of water dissociation.

[0110] Ⅱ)、Carbonation simulation analysis

[0111] Carbonation simulation analysis, using Plumed package to process the hills file obtained in S2 simulation, to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, finally obtain the reaction route of carbonation. Figure 13 It is shown that proton transfer reduces the energy barrier of carbonation, and the most stable form of carbon species is bicarbonate.

[0112] Calcium dissolution simulation analysis, using Plumed package to process the hills file obtained in S2 simulation, to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, finally obtain the reaction route of calcium dissolution. Figure 14 It is shown that in the early stage of calcium dissolution, carbonic acid significantly reduces the energy barrier of calcium dissolution, promoting the dissolution of calcium; in the later stage of calcium dissolution, carbonic acid changes the dissolution kinetics of calcium.

[0113] Carbon dioxide activation simulation analysis, using Plumed package to process the hills file obtained in S2 simulation, to obtain the free energy surface of the reaction, record the energy local minimum of the surface and the reaction energy barrier between the energy local minimum, finally obtain the reaction route of carbon dioxide activation. Figure 15 It is shown that due to the proton exchange effect, active hydroxyl groups appear in the solution after calcium dissolution, which have strong electron-donating ability and can activate carbon dioxide.

[0114] S4、Conclusion

[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] Reaction mechanism of early carbonation of CS, including:

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

[0119] Through the above technical measures, after simulation, the key physicochemical processes of hydration and carbonation, such as molecular dissociation, proton transfer, calcium dissolution, etc. are mastered. Thus, the person 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 by regulating the solution environment of carbonation, so as to realize the enhancement of wollastonite carbonation reaction and high-performance wollastonite carbon sequestration material.

[0120] The calculation parameters involved in the method are as follows: all simulations use VASP and CP2K calculation programs. VASP geometry optimization parameters: using generalized gradient approximation functional (GGA) to approximate exchange related potential, four crystal models are continuously optimized to energy difference and force difference less than 1*10-5eV / atom and 0.02eV / A, the cutoff energy is 500eV, and 2*2*1 Gamma point sampling is used. The projection augmented plane wave (PAW) method is used to describe the atomic pseudo potential, O2s22p4, Si3s23p2, Ca3s23p64s2, H1s1. In addition, DFT-D3 dispersion correction is selected to consider van der Waals correction (VDW). CP2K dynamics parameters: use PACKMOL code to generate water layer. In the simulation, PBE function and DFT-D3 correction are used, and gamma point is used to sample reciprocal space. Core electrons are described using Goedecker-Teter-Hutter (GTH) pseudo potential, and valence electron density is established on the basis of double Zeta valence polarization (DZVP-MOLOPT-SR-GTH) basis set and auxiliary plane wave basis set with a cutoff energy of 500Ry. The convergence criteria for energy and self-consistent field are set to 10-10 and 10-5 Hartree respectively.

[0121] The present application first screens the most reasonable surface model according to the size of the surface energy, and builds different models for hydration and carbonation reaction on the basis of the model.

[0122] Secondly: for hydration and carbonation reaction, set the parameters of ab initio molecular dynamics simulation software CP2K and metadynamics Plumed software package.

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

[0124] Finally, based on the analysis results, the early reaction mechanism and route of hydration and carbonation are summarized.

[0125] The application innovatively reveals the reaction free energy surface through metadynamics, thereby quantitatively understanding the reaction path, and providing an idea of digital research for the design of cement-based materials. Through the study of the adsorption behavior of water molecules and carbon dioxide and carbonic acid molecules on the CS surface and the interaction between the molecules and the surface, the carbonation mechanism of wollastonite is analyzed from the nanoscale, and the hydration mechanism and carbonation mechanism are revealed, which has important significance for realizing high carbonation performance and high stability carbon storage materials and understanding the carbonation behavior.

[0126] It should be noted that the above specific embodiments are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art should understand that, on the basis of the disclosed technology content of the present application, various modifications, equivalent replacements, changes, etc. can be made to the present application. However, as long as these changes do not deviate from the spirit of the present application, they should be within the protection scope of the present application. In addition, some terms used in the present application specification and claims are not limited, but 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 using first-principles software, and selection of reasonable structures based on surface energy; 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 cross-section models; The setup of hydration simulations, including ab initio molecular dynamics setup for hydration simulations and metadynamics setup for water dissociation simulations; The setup of carbonation simulation, including metadynamic setup of carbonic acid dissociation, calcium dissolution and carbon dioxide activation simulation; 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; The CS surface cross-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; The hydration simulation model is based on the terminal 3 of the CS(001) surface. A water layer consisting of 60 water molecules is placed 3Å away from the terminal surface, and the vacuum layer thickness is 20Å. The model of the 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; The carbonization simulation model includes: The model of carbonic acid dissociation uses the terminal 3 of the CS(001) surface as the base, and places a water layer consisting of 59 water molecules and a carbonic acid molecule 3 Å away from the end surface. The vacuum layer thickness is 20 Å. For 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, which is used as the initial structure of the carbon dioxide activated model.

2. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: In step S2, the structure of the CS surface cross-section model is optimized by using simulation software VASP, CP2K and Plumed software package. The ab initio molecular dynamics and metadynamics simulation methods are as follows: a. Settings for CS surface cross-section model structure optimization: The CS surface cross-section model was converted into a .vasp format readable by VASP. Four input files were set for the simulation optimization software VASP: 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, a self-consistent calculation of the structure optimization was performed using the simulation optimization software VASP. The model was optimized for different surface structures, and finally a stable structure data file after structure optimization was obtained. The structural stability was 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. Hydration simulation settings, 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 using the simulation optimization software CP2K, and then performing a hydration molecular dynamics simulation of the surface to obtain the final hydration state in thermodynamic equilibrium; The water dissociation simulation was set up by converting the CS surface cross-section model 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 were set up. For the water dissociation process, a specific hydrogen-oxygen bond length was used as a collective variable to scan the free energy surface of the water dissociation process. c. Carbonization simulation settings, including: The carbonic acid dissociation simulation was 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 carbonic acid dissociation process with a specific hydrogen-oxygen distance as a set variable for the carbonic acid dissociation process; The calcium dissolution simulation was set up by converting the CS surface cross-section model 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 were set up. For the calcium dissolution process, the calcium-oxygen coordination number was used as a collective variable to scan the free energy surface of the calcium dissolution process. The CO2 activation simulation was set up by converting the CS surface cross-section model 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 were set up. For the CO2 activation process, the free energy surface of the CO2 activation process was scanned with a specific carbon-oxygen distance as a collective variable.

3. 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: obtain the pdb trajectory file in the hydration simulation and perform trajectory, radial distribution function, and root mean square displacement analysis on the file; For the analysis of water dissociation simulation, 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 of the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction path of water dissociation; II) Analysis of carbonization simulation Analysis of the carbonic acid dissociation simulation: 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 path 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 of the surface and the reaction energy barriers between the local energy minima, and finally obtain the reaction path of calcium dissolution; The analysis of the carbon dioxide activation simulation used the Plumed software package to process the hills file obtained from 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 carbon dioxide activation.

4. The method for analyzing the carbonization mechanism of wollastonite based on nanoscale according to claim 1, characterized in that: The reaction mechanism of early hydration of CS includes: The adsorption behavior and migration of water molecules and the interaction between surface atoms and water molecules; the pathways and mechanisms of water dissociation, including direct dissociation and proton transfer-promoted dissociation; and The reaction mechanism of early carbonization of CS includes: The dissociation route and mechanism of carbonate 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 carbonate molecules; the activation route and mechanism of carbon dioxide.

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