Method for predicting difference of initial carbonation reactions of C2S with different crystal forms

Abstract

The invention relates to a method for predicting initial carbonation reaction difference of C2S with different crystal forms. Relates to an analysis method for C2S initial carbonation reaction difference. The method comprises the following steps: S1, constructing a model; S2, setting the model; S3, analyzing a result; and S4, drawing a conclusion to obtain the active degrees of carbonation reactions of different crystal forms of CO2 and HCO3 in different reaction periods. According to the method, the current situation that in the prior art, the key step mechanism of activation of CO2 molecules and HCO3 <-> ions in C2S carbonization is difficult to represent and predict is solved, the reaction free energy surface is innovatively revealed through meta-dynamics, so that the reaction path is quantitatively known, and a digital research thought is creatively provided for cement-based material design. By researching the initial reaction of carbon dioxide and carbonic acid molecules on the surfaces of different crystal forms of C2S and the interaction between the molecules and the surfaces, the acid-activated hydration mechanism and carbonization mechanism are disclosed, which are of great significance for realizing high-carbonization performance and high-stability carbon sequestration materials and understanding the carbonization behavior of the carbon sequestration materials.

Description

Technical Field

[0001] The invention relates to the field of cement in building materials, and in particular to a method for analyzing and predicting the difference of C2S initial carbonation reaction. Background Art

[0002] Climate and ecological changes caused by global warming are becoming increasingly serious. Therefore, reducing the CO2 content in the atmosphere is crucial to slowing down global warming. Among many solutions, CO2 mineralization is considered to be a cost-effective method. The principle of this method is to use CO2 to react chemically with metal cations (such as magnesium, calcium and iron) to form stable carbonate minerals to achieve permanent storage of CO2. The carbonation activity of dicalcium silicate (C2S) has attracted attention. In order to reveal the kinetic mechanism of its carbonation reaction, a large number of researchers have focused on regulating the carbonation reaction rate of C2S. With the continuous breakthroughs in experimental tests, researchers' understanding of traditional calcium silicate phases has gradually shifted from macroscopic surface phases to deeper mechanism discussions, while there are fewer studies on the hydration nature of new dicalcium silicate cement. Existing experimental studies mainly study the carbonation reaction activity of different calcium silicate mineral phases by measuring the heat of carbonation reaction and the mechanical properties of carbonation products. Although these test methods can evaluate the differences in carbonation activity of different mineral phases, they still cannot reveal the corresponding carbonation reaction mechanism.

[0003] In recent years, the increasingly mature atomic simulation technology has been widely used in the complex field of cement chemistry. How to use atomic simulation technology to analyze the essential relationship between hydration activity and surface microstructure at the nanoscale, to make up for the lack of understanding of microstructure, to understand the differences in carbonization reaction rates from the source, and then to provide theoretical guidance for carbon fixation and carbon maintenance has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a method for predicting the differences in the initial carbonation reactions of C2S of different crystalline forms by revealing the carbonization reaction mechanism at a nanoscale, thereby qualitatively understanding the electron transfer and bonding conditions.

[0005] The present invention provides a method for predicting the difference of initial carbonation reaction of C2S with different crystalline forms, comprising the following steps: S1. Model construction, Construction of surface CO2 molecules and activated HCO in different crystalline C2S by different surface carbonization configurations 3- Ion adsorption model, that is, using material model building software to build the basic unit cell model of C2S, and then changing the CO2 reaction and HCO 3- Reaction configuration, obtaining different carbonation reaction mechanism surfaces; S2. Model settings, Molecular dynamics simulations were performed to analyze the surface structures of CO2 molecules and HCO 3- Optimization of ion activation sites; obtaining structural models of different crystal surfaces after initial carbonation reactions over a period of time; S3. Result analysis, S3.1, perform structural characteristics analysis, S3.1.1 Analysis of initial carbonation results on different crystal surfaces by comparing CO2 molecules and HCO 3- The initial carbonation activity can be determined by the bond length, bond angle, Si-O bond length and HO radial distribution function of the ions; S3.1.2. Thermodynamic energy barrier analysis to reveal the relationship between β-C2S(100) / H2O-CO2 and γ-C 2 S(010) / H 2 O-CO 2 , β-C 2 S(100) / H 2 O-HCO 3− and γ-C2S(010) / H2O-HCO 3− The initial carbonation reaction mechanism of the system; S3.2. Charge transfer analysis of CO2 molecules and HCO after activation on different C2S surfaces 3- Charge transfer of ionic configurations reveals differences in initial carbonation reactivity by comparing charge transfer. S4. Conclusion Different crystal forms of CO2 and HCO 3− The activity of the carbonation reaction at different reaction stages.

[0006] Furthermore, the step S1 uses material model building software to build a basic unit cell model of C2S, specifically: Using the surface model of the β-C2S crystal plane index (100) of activated CO2 molecules, the vacuum layer is 1.0 nm, the water layer is 1.0 nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other is placed in the bulk solution. A model of a×b×c=13.63×9.38×44.00Å is established; To activate HCO 3- ion β-C2S crystal plane index (100) surface model, vacuum layer is 2.0nm, one H2O molecule is replaced by HCO 3− Ion substitution, a model of a×b×c=13.63×9.38×44.00Å was established; Using the surface model of the crystal plane index (100) of γ-C2S of activated CO2 molecules, the vacuum layer is 2.0nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other CO2 molecule is placed in the bulk solution, to establish a model of a×b×c=13.56×10.16×44.00Å; To activate HCO 3- ion γ-C2S crystal plane index (100) surface model, vacuum layer is 2.0nm, one H2O molecule is replaced by HCO 3− After ion substitution, a model of a×b×c=13.56×10.16×44.00Å was established.

[0007] Furthermore, the step S2 performs molecular dynamics calculations using simulation optimization software cp2k, and the output files include cp2k.out and structure pdb files.

[0008] Furthermore, in step S3.1.1, after the initial carbonation, CO2 molecules and HCO 3- The structural changes of the ions are as follows: On the β-C2S(100) surface, CO2 molecules gradually approach the surface, deflect and approach the surface O ions, and the activated CO2 molecules change from a straight line to a bent shape, and the Si-Os bond corresponding to the Si bonded to the surface O ions is elongated; On the surface of γ-C2S(100), CO2 molecules are activated by binding to H2O molecules to form HCO 3- The surface silicon-oxygen tetrahedron is hydroxylated. When the H2O molecule dissociates, the dissociated hydroxyl group combines with the CO2 molecule, the C-Ox bond length is elongated, and the corresponding Si-Os bond is elongated. On the β-C2S(100) surface, HCO 3- The H in the ion gradually approaches the surface O ion, the C-O1 and C-Ox in the ion are shortened and elongated, the corresponding Si-Os bond is elongated, and CO3 2- The ions bind to the surface Ca and H2O molecules; On the γ-C2S(100) surface, H2O molecules are close to HCO 3− When the H in the ion is removed, hydrogen transfer occurs, and H is transferred from the body to the H2O molecule, and one H on the original H2O is transferred to another H2O molecule.

[0009] Furthermore, in step S3.1.2, mild metadynamics simulation is used as an enhanced sampling measure to obtain the thermodynamic energy barriers required for the carbonation pathways of different crystalline forms, and the two-dimensional potential energy surface diagram and atomic structure are studied to explain the differences between the two mechanisms.

[0010] Furthermore, the difference in initial carbonation reaction activity disclosed in step S3.2 is specifically: In the β-C2S(100) / H2O-CO2 system, CO2 molecules gain 0.097e electrons from surface ions and H2O molecules, and surface Ca ions lose 0.039e electrons; In the γ-C2S(100) / H2O-CO2 system, after the CO2 molecule is activated by the H2O molecule, the corresponding O1, O2 and Ow continuously gain electrons, while the C in the CO2 molecule and the surface Ca ions lose electrons; In β-C2S(100) / H2O-HCO 3- In the system, the dissociated H and CO3 2− The ions begin to transfer charge, O2 transfers charge with the surface Ca ions, surface H and a neighboring H2O molecule, CO3 2− The binding state of O1 in the ion changes from binding with three H2O molecules to binding with one H2O molecule and surface H; In γ-C2S(100) / H2O-HCO 3- In the system, the charge is transferred from the surface Ca ions and the H atoms in the surrounding H2O molecules to HCO 3− On the O ion, HCO 3− The charge in the ion is transferred from C to the three O atoms.

[0011] Furthermore, the conclusion obtained in step S4 is specifically: In the β-C2S(100) / H2O-CO2 system, CO2 forms a stable bicarbonate complex with surface Ca by reacting with surface O ions; In the γ-C2S(100) / H2O-CO2 system, CO2 reacts with O ions in water to form HCO 3- and combines with surface Ca to form bicarbonate complex; In β-C2S(100) / H2O-HCO 3− The initial carbonation reaction in the system is active, and the water molecules show stronger solvation, forming a stable carbonate complex layer, which hinders the carbonation reaction; In γ-C2S(100) / H2O-HCO 3− Proton transfer occurs with water molecules in the system, and hydrogen bonds occur with water molecules to form a stable solvation structure.

[0012] Furthermore, the VASP calculation program was used, and the geometric structure optimization parameters were: the generalized gradient approximation functional was used to approximate the exchange-correlation potential, and different crystal models were optimized to an energy difference and a force difference of less than 1×10 -5eV / atom and 0.03eV / Å, with a cutoff energy of 600eV.

[0013] Furthermore, the CHGCAR, AECCAR0 and AECCAR2 files obtained after VASP calculation are post-processed to obtain charge files.

[0014] The present invention solves the problem that it is difficult to characterize CO2 molecules and HCO in C2S carbonization in the prior art. 3- In view of the current situation that the mechanism of the key step of ion activation is difficult to predict, the reaction free energy surface is innovatively revealed through metadynamics, so as to quantitatively understand the reaction path, and provide a pioneering digital research idea for the design of cement-based materials. By studying the initial reaction of carbon dioxide and carbonic acid molecules on the surfaces of different C2S crystal forms and the interaction between the molecules and the surface, their acid-induced 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. The prediction method of the present invention reveals the carbonization reaction mechanism at the nanoscopic level, and can qualitatively understand the electron transfer and bonding situation, which provides a pioneering digital research idea for the design of cement-based materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall technical route of the present invention, Figure 2 is a flow chart of the prediction method of the present invention, Figure 3 It is the activation model of surface CO2 molecules and activated HCO3- ions of two different crystalline forms of C2S. Figure 4 The atomic structure analysis of the surface CO2 molecules and HCO3- ion adsorption model of two different crystalline C2S, Figure 5 is the WT-MetaD sampling thermodynamic barrier diagram of the initial carbonation configuration of the two C2S crystal surfaces. Figure 6 It simulates the reaction process between CO2 molecules and HCO3- ions on different crystal surfaces. Figure 7 are the charge transfer diagrams of the four configurations. DETAILED DESCRIPTION

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The present invention provides a method for predicting the difference of initial carbonation reaction of C2S with different crystalline forms, comprising the following steps: S1. Model construction, Construction of surface CO2 molecules and activated HCO in different crystalline C2S by different surface carbonization configurations 3- Ion adsorption model, that is, using material model building software to build the basic unit cell model of C2S, and then changing the CO2 reaction and HCO 3- Reaction configurations give different carbonation reaction mechanism surfaces.

[0021] Step S1 uses material model building software to build a basic unit cell model of C2S, specifically: Using the surface model of the β-C2S crystal plane index (100) of activated CO2 molecules, the vacuum layer is 1.0 nm, the water layer is 1.0 nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other is placed in the bulk solution. A model of a×b×c=13.63×9.38×44.00Å is established; To activate HCO 3- ion β-C2S crystal plane index (100) surface model, vacuum layer is 2.0nm, one H2O molecule is replaced by HCO 3− Ion substitution, a model of a×b×c=13.63×9.38×44.00Å was established; Using the surface model of the crystal plane index (100) of γ-C2S of activated CO2 molecules, the vacuum layer is 2.0nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other CO2 molecule is placed in the bulk solution, to establish a model of a×b×c=13.56×10.16×44.00Å; To activate HCO 3- The surface model of the γ-C2S crystal plane index (100) of the ion, the vacuum layer is 2.0nm, and a H2O molecule is replaced by HCO 3− After ion substitution, a model of a×b×c=13.56×10.16×44.00Å was established.

[0022] S2, simulation settings, Molecular dynamics simulations were performed to analyze the surface structures of CO2 molecules and HCO 3- Optimization of ion activation sites; obtaining structural models of different crystal surfaces after an initial carbonation reaction over a period of time; the reaction time is generally 20ps.

[0023] The computer simulation software used in the method of this embodiment is the cp2k software package. The C2S structural models of the above two different surface terminals are converted to set the inp input files of the simulation optimization software cp2k: the file describing the architecture, the pseudopotential file describing the elements, and the calculation control parameter file. Then, the molecular dynamics calculation is performed by the simulation optimization software cp2k. For different surface structures, CO2 molecules and HCO 3- Optimization of the model of ion activation sites. Its output files mainly include cp2k.out, structure pdb files, etc.

[0024] The computer simulation software used for charge transfer analysis is the VASP software package. VASP is a software package based on density functional theory that uses the plane wave pseudoformula (or suffixed projection wave) method for ab initio molecular dynamics and first-principles electronic structure calculations. VASP includes four input files: INCAR (calculation control parameter file), KPOINTS (K-point sampling setting file), POSCAR (description system architecture file) and POTCAR (pseudopotential file). Its output files mainly include OUTCAR, CHG, CHGCAR, WAVECAR, DOSCAR, CONTCAR, EIGENVAL, OSZICAR, etc. For the output files, you can use script programs or auxiliary software to process them to obtain the desired results.

[0025] S3. Result analysis, S3.1, perform structural characteristics analysis, S3.1.1 Analysis of initial carbonation results on different crystal surfaces by comparing CO2 molecules and HCO 3- The initial carbonation activity can be determined by the bond length, bond angle, Si-O bond length and HO radial distribution function of the ions.

[0026] In this embodiment, the surface CO2 molecules and HCO 3- Ion adsorption model, see Figure 3 By comparing CO2 molecules and HCO 3- The initial carbonation activity can be determined by the bond length, bond angle, Si-O bond length and HO radial distribution function of the ions, see Figure 4 . Figure 4 Shows the activated CO2 molecule and HCO 3- The structural changes of the ions. On the surface of β-C2S(100), as the CO2 molecules gradually approach the surface, they deflect and approach the surface O ions. The activated CO2 molecules change from straight to bent, and the Si-Os bonds corresponding to the Si bonded to the surface O ions are elongated. On the surface of γ-C2S(100), CO2 molecules are activated by binding to H2O molecules to form HCO 3- When the H2O molecules dissociate, the dissociated hydroxyl groups combine with CO2 molecules, the C-Ox bond length is elongated, and the corresponding Si-Os bond is elongated to form HCO 3- The O ions in the water combine with the Ca on the surface to form a bicarbonate complex.

[0027] Further, after the initial carbonation in step S3.1.1, CO2 molecules and HCO 3- The structural changes of the ions are as follows: On the β-C2S(100) surface, as the CO2 molecules gradually approach the surface, they deflect and move closer to the surface O ions. The activated CO2 molecules change from a straight shape to a bent shape, and the Si-Os bonds corresponding to the Si bonded to the surface O ions are elongated.

[0028] On the surface of γ-C2S(100), CO2 molecules are activated by binding to H2O molecules to form HCO 3- The surface silicon-oxygen tetrahedron is hydroxylated. When the H2O molecule dissociates, the dissociated hydroxyl group combines with the CO2 molecule, the C-Ox bond length is elongated, and the corresponding Si-Os bond is elongated; the formed HCO 3- The O ions in the water combine with the Ca on the surface to form a bicarbonate complex.

[0029] On the β-C2S(100) surface, as HCO 3-The H in the ion gradually approaches the surface O ion, the C-O1 and C-Ox in the ion are shortened and elongated, the corresponding Si-Os bond is elongated, and the HCO at the interface 3- The H ions in the ions dissociate, CO3 2- ions bind to the surface Ca and H2O molecules, and the dissociated CO3 2- The first radial distribution peak between the O in the ion and the H atom in the H2O molecule appears at 1.68Å, indicating that CO3 2- Interaction of the O atoms in the ion with the H atoms in the nearest neighbor H2O molecules.

[0030] On the γ-C2S(100) surface, when H2O molecules gradually approach HCO 3− When the H in the ion is removed, hydrogen transfer occurs, and H is transferred from the body to the H2O molecule, and one H on the original H2O is transferred to another H2O molecule. 2- The first radial distribution peak between the O in the ion and the H atom in the H2O molecule appears at 1.68Å, indicating that CO3 2- The oxygen in the ion is tightly bound to the hydrogen atom in the nearest neighboring H2O molecule. 2- There are an average of 2.76 H atoms bound to the first solvation coordination shell of the O ion in the ion, which is similar to the β-C2S(100) / H2O-HCO 3− Compared with the system, water molecules show a stronger solvation effect.

[0031] S3.1.2. Thermodynamic energy barrier analysis to reveal the relationship between β-C2S(100) / H2O-CO2 and γ-C 2 S(010) / H 2 O-CO 2 , β-C 2 S(100) / H 2 O-HCO 3− and γ-C2S(010) / H2O-HCO 3− The initial carbonation reaction mechanism of the system; In step S3.1.2, mild metadynamics (WT-MetaD) simulation was used as an enhanced sampling measure to obtain the thermodynamic energy barriers required for the carbonation pathways of different crystalline forms, and the two-dimensional potential energy surface diagram and atomic structure were studied to explain the differences between the two mechanisms.

[0032] Specifically, mild metadynamics (WT-MetaD) simulations were used as an enhanced sampling method to reveal the relationship between β-C2S(100) / H2O-CO2, γ-C2S(010) / H2O-CO2, β-C2S(100) / H2O-HCO 3− and γ-C2S(010) / H2O-HCO 3−The initial carbonation reaction mechanism of the system. WT-MetaD simulation is implemented by the CP2K / Quickstep code and the PLUMED code. The WT-MetaD parameters are determined according to the research content and are set accordingly in different systems. Figure 5 It can be concluded that different crystalline forms of C2S react with CO2 / HCO 3- The reaction paths are obviously different, and the γ-C2S(100) / H2O-CO2 reaction has the most intermediate states and the reaction path is more complicated. Figure 6 The reaction path structure and energy barrier are given by Figure 5 Expand. Figure 6 It can be concluded that in the β-C2S(100) / H2O-CO2 system, the surface O ions provide activation sites for CO2 molecules at the interface. The activated CO2 molecules combine with the surface O ions and Ca ions to form metal carbonate complexes anchored on the surface. The CO2 molecule needs to undergo three state transitions during activation. As the CO2 molecule gradually approaches the surface, the distance between C-Os decreases to 1.99Å, the CO2 molecule bends, and the corresponding C-O2 bond length is elongated to 1.21Å. From state A to B, an energy barrier of 11.32kJ / mol needs to be overcome. When the distance between C and the surface O ions in the CO2 molecule decreases to 1.43Å, the corresponding free energy decreases to -106.67kJ / mol, reaching a stable state C. In the γ-C2S(010) / H2O-CO2 system, the activity of the surface O ions is low, and the CO2 molecules at the interface are activated by combining with H2O molecules. The entire initial carbonation reaction process can be divided into the activation stage (A to C) and the complexation stage (C to E). In the activation stage, the CO2 molecule gradually approaches the H2O molecule, and the H2O molecule dissociates to form an isolated hydroxyl group. At this time, the system is in an unstable state B, resulting in a free energy increase of 1.26 kJ / mol. When CO2 combines with the hydroxyl group, the isolated CO2 molecule is converted into HCO 3− ions. Newly generated HCO 3− The ions combine with the surrounding H2O molecules through hydrogen bonds, reaching a relatively stable state, and the corresponding free energy is reduced to -80.52 kJ / mol. 3− The ions gradually approach the surface Ca ions to form bicarbonate complexes, and the corresponding C-O2 bond length further increases to 1.28Å, and the system reaches a stable state.

[0033] In β-C2S(100) / H2O-HCO 3- In this system, HCO 3− The H in the ion dissociates from the body, and the dissociated H combines with the surface oxygen ions. The dissociated CO3 2−One of the O ions in the HCO ion combines with the surface Ca ion, and a relatively stable state is reached at this time, with a corresponding free energy of -43.52 kJ / mol. 3− After the ion dissociates, the corresponding O1 is affected by three neighboring interactions, and O3 is affected by an isolated hydroxyl group and H2O molecules. The corresponding C-O1 bond length is shortened from 1.31Å to 1.25Å. The solvation of H2O molecules further stabilizes the dissociated structure, and the corresponding free energy decreases by 4.25kJ / mol. 2− The ions are attracted by the dissociated H, and the structure of O1 is further stabilized under the combined action of the surface H and the H atoms in the H2O molecules, and the corresponding free energy continues to decrease by 1.56 kJ / mol. 3− In the system, HCO 3− The ions dissociate at the interface, and the dissociated H is transferred from HCO 3− The ion transfers to a neighboring H2O molecule, forming a solvated CO3 2− ions. In state A, HCO 3− The O3 in the ion combines with the surface Ca ion, and the corresponding Ca-O3 distance is 2.70Å, forming a bicarbonate complex with a corresponding free energy of -27.04kJ / mol. As the Ca-O3 distance increases to 3.16Å, the free energy increases by 4.39kJ / mol, and it is in an unstable state. In the transition from state B to state C, the Ca-O3 distance increases to 3.91Å, and the corresponding free energy decreases to -50.07kJ / mol, reaching a stable state.

[0034] S3.2. Charge transfer analysis of CO2 molecules and HCO after activation on different C2S surfaces 3- The charge transfer of ion configurations reveals the difference in initial carbonation reaction activity by comparing the charge transfer. The charge transfer of CO2 molecules and HCO3- ion configurations after surface activation on C2S reveals the difference in initial carbonation reaction activity by comparing the charge transfer. Figure 7It can be seen that in the β-C2S(100) / H2O-CO2 system, when the state changes from A to B, O1 and O2 in the CO2 molecule obtain electrons from the surface ions and H2O molecules, and the amount of electrons transferred from C decreases. From the isolated CO2 molecule to the carbonate complex formed after activation, the CO2 molecule obtains 0.097e electrons from the surface ions and H2O molecules, and the surface Ca ions lose 0.039e electrons. In the γ-C2S(100) / H2O-CO2 system, during the entire reaction process, after the CO2 molecule is activated by the H2O molecule, the corresponding O1, O2 and Ow continue to obtain electrons, while the C in the CO2 molecule and the surface Ca ions lose electrons. This charge transfer mechanism promotes the formation of the bicarbonate complex.

[0035] In the β-C2S(100) / H2O-HCO3- system, from state A to state B, the dissociated H and CO32- ions begin to transfer charge, and the corresponding H loses 0.187e electrons again. In state B, O2 transfers charge with surface Ca ions, surface H and a neighboring H2O molecule, but the charge of O2 decreases by 0.076e, which is consistent with the charge transfer trend of surface Ca ions. From state B to state C, the binding state of O1 in CO32- ions changes from binding with three H2O molecules to binding with one H2O molecule and surface H, and the charge decreases by 0.046e. In the γ-C2S(100) / H2O-HCO3- system, the charge is transferred from the surface Ca ions and the H atoms in the surrounding H2O molecules to the O of the HCO3- ion, and the charge in the HCO3- ion transfers from C to three O. The charge transfer of the surface Ca ion decreased by 0.020e, the charge transfer of C decreased by 0.036e, the charges of the three O ions decreased, and the charge transfer of the dissociated H decreased by 0.218e. 2− The ions bind to the surface ions and other H2O molecules in the aqueous solution through the H2O molecules in the solvent layer.

[0036] S4. Conclusion Different crystal forms of CO2 and HCO 3− The activity of the carbonation reaction at different reaction stages.

[0037] 1. In the β-C2S(100) / H2O-CO2 system, due to the strong activity of surface oxygen ions, the CO2 molecules at the interface are activated by the surface oxygen ions, the corresponding CO bonds are elongated, the OCO bond angle is reduced, and the surface Si-O bond length is elongated after activation. The activated CO2 molecules combine with the surface Ca and O ions to form a stable carbonate complex.

[0038] 2. In the γ-C2S(010) / H2O-CO2 system, the activity of the surface O ions is lower than that of the β-C2S(100) surface, and the H2O molecules at the interface provide activation sites for the CO2 molecules. The O atoms in the H2O molecules induce the CO2 molecules to bend, and at the same time, the H2O molecules dissociate. The dissociated hydroxyl groups combine with the bent CO2 molecules to form HCO3− ions. The dissociated H combines with the surface O ions to hydroxylate the silicon-oxygen tetrahedrons on the surface. The HCO3− ions formed after activation combine with the surface Ca ions to form bicarbonate complexes.

[0039] 3. In the β-C2S(100) / H2O-HCO3− system, HCO3− ions are attracted by surface ions and combine with surface Ca ions. At the same time, H in HCO3− ions is attracted by surface O ions and dissociates. The CO bonds after dissociation are lengthened and shortened. After dissociation, HCO3− ions combine with neighboring H2O molecules and surface Ca ions to form carbonate complexes.

[0040] 4. In the γ-C2S(010) / H2O-HCO3− system, the HCO3− ions first combine with the surface Ca ions. Due to the low activity of the surface O ions, the H in the HCO3− ions does not combine with the surface O. The H in the HCO3− ions is attracted by the O atoms in the H2O molecules and hydrogen transfer occurs. Each O in the dissociated CO32− forms hydrogen bonds with the surrounding three H2O molecules, forming a stable solvation structure.

[0041] The calculation parameters involved in this method are as follows: All simulations were performed using the VASP calculation program, and its geometry optimization parameters were as follows: 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 0.03eV / Å, respectively, with a cutoff energy of 600eV. For the β-C2S(100) / H2O-(CO2 / HCO3−) and γC2S(010) / H2O-(CO2 / HCO3−) systems, 2×3×1 and 2×2×1 K points were used, respectively. The projected enhanced plane wave (PAW) method was used to describe the atomic pseudopotentials, which were O2s22p4, Si3s23p2, Ca3s23p64s2, C2s22p2, and H1s1. In addition, DFT-D3 dispersion correction was used to consider the van der Waals correction (VDW).

[0042] Furthermore, the CHGCAR, AECCAR0 and AECCAR2 files obtained after VASP calculation are post-processed to obtain charge files.

[0043] 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 predicting the differences in the initial carbonation reactions of C2S of different crystalline forms, characterized in that: The following steps are involved: S1. Model construction, Construction of surface CO2 molecules and activated HCO in different crystalline C2S by different surface carbonization configurations 3- Ion adsorption model, that is, using material model building software to build the basic unit cell model of C2S, and then changing the CO2 reaction and HCO 3- Reaction configuration, obtaining different carbonation reaction mechanism surfaces; S2. Model settings, Molecular dynamics simulations were performed to analyze the surface structures of CO2 molecules and HCO 3- Optimization of ion activation sites; obtaining structural models of different crystal surfaces after initial carbonation reactions over a period of time; S3. Result analysis, S3.1, perform structural characteristics analysis, S3.1.1 Analysis of initial carbonation results on different crystal surfaces by comparing CO2 molecules and HCO 3- The bond length, bond angle, Si-O bond length and HO radial distribution function of the ions are used to determine the initial carbonation activity; S3.1.

2. Thermodynamic energy barrier analysis to reveal the relationship between β-C2S(100) / H2O-CO2 and γ-C 2 S(010) / H 2 O-CO 2 , β-C 2 S(100) / H 2 O-HCO 3− and γ-C2S(010) / H2O-HCO 3− The initial carbonation reaction mechanism of the system; S3.

2. Charge transfer analysis of CO2 molecules and HCO after activation on different C2S surfaces 3- Charge transfer of ionic configurations reveals differences in initial carbonation reactivity by comparing charge transfer. S4. Conclusion Different crystal forms of CO2 and HCO 3− The activity of the carbonation reaction at different reaction stages.

2. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 1, characterized in that, The step S1 uses material model building software to build a basic unit cell model of C2S, specifically: Using the surface model of the β-C2S crystal plane index (100) of activated CO2 molecules, the vacuum layer is 1.0 nm, the water layer is 1.0 nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other is placed in the bulk solution. A model of a×b×c=13.63×9.38×44.00Å is established; To activate HCO 3- ion β-C2S crystal plane index (100) surface model, vacuum layer is 2.0nm, one H2O molecule is replaced by HCO 3− Ion substitution, a model of a×b×c=13.63×9.38×44.00Å was established; Using the surface model of the crystal plane index (100) of γ-C2S of activated CO2 molecules, the vacuum layer is 2.0nm, and two H2O molecules are replaced by two CO2 molecules, one of which is placed in the adjacent surface layer and the other CO2 molecule is placed in the bulk solution, to establish a model of a×b×c=13.56×10.16×44.00Å; To activate HCO 3- ion γ-C2S crystal plane index (100) surface model, vacuum layer is 2.0nm, one H2O molecule is replaced by HCO 3− After ion substitution, a model of a×b×c=13.56×10.16×44.00Å was established.

3. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 1, characterized in that: The step S2 performs molecular dynamics calculations using simulation optimization software cp2k, and the output files include cp2k.out and structure pdb files.

4. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 2, characterized in that, After the initial carbonation of step S3.1.1, CO2 molecules and HCO 3- The structural changes of the ions are as follows: On the β-C2S(100) surface, CO2 molecules gradually approach the surface, deflect and approach the surface O ions, and the activated CO2 molecules change from a straight line to a bent shape, and the Si-Os bond corresponding to the Si bonded to the surface O ions is elongated; On the surface of γ-C2S(100), CO2 molecules are activated by binding to H2O molecules to form HCO 3- The surface silicon-oxygen tetrahedron is hydroxylated. When the H2O molecule dissociates, the dissociated hydroxyl group combines with the CO2 molecule, the C-Ox bond length is elongated, and the corresponding Si-Os bond is elongated. On the β-C2S(100) surface, HCO 3- The H in the ion gradually approaches the surface O ion, the C-O1 and C-Ox in the ion are shortened and elongated, the corresponding Si-Os bond is elongated, and CO3 2- ions bind to surface Ca and H2O molecules; On the γ-C2S(100) surface, H2O molecules are close to HCO 3− When the H in the ion is removed, hydrogen transfer occurs, and H is transferred from the body to the H2O molecule, and one H on the original H2O is transferred to another H2O molecule.

5. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 2, characterized in that, In step S3.1.2, mild metadynamics simulation is used as an enhanced sampling measure to obtain the thermodynamic energy barriers required for the carbonation pathways of different crystalline forms, and the two-dimensional potential energy surface diagram and atomic structure are studied to explain the differences between the two mechanisms.

6. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 2, characterized in that, The difference in the initial carbonation reaction activity disclosed in step S3.2 is specifically: In the β-C2S(100) / H2O-CO2 system, CO2 molecules gain 0.097e electrons from surface ions and H2O molecules, and surface Ca ions lose 0.039e electrons; In the γ-C2S(100) / H2O-CO2 system, after the CO2 molecule is activated by the H2O molecule, the corresponding O1, O2 and Ow continuously gain electrons, while the C in the CO2 molecule and the surface Ca ions lose electrons; In β-C2S(100) / H2O-HCO 3- In the system, the dissociated H and CO3 2− The ions begin to transfer charge, O2 transfers charge with the surface Ca ions, surface H and a neighboring H2O molecule, CO3 2− The binding state of O1 in the ion changes from binding with three H2O molecules to binding with one H2O molecule and surface H; In γ-C2S(100) / H2O-HCO 3- In the system, the charge is transferred from the surface Ca ions and the H atoms in the surrounding H2O molecules to HCO 3− On the O ion, HCO 3− The charge in the ion is transferred from C to the three O atoms.

7. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 2, characterized in that, The conclusion obtained in step S4 is specifically: In the β-C2S(100) / H2O-CO2 system, CO2 forms a stable bicarbonate complex with surface Ca by reacting with surface O ions; In the γ-C2S(100) / H2O-CO2 system, CO2 reacts with O ions in water to form HCO 3- and combines with surface Ca to form bicarbonate complex; In β-C2S(100) / H2O-HCO 3− The initial carbonation reaction in the system is active, and the water molecules show stronger solvation, forming a stable carbonate complex layer, which hinders the carbonation reaction; In γ-C2S(100) / H2O-HCO 3− Proton transfer occurs with water molecules in the system, and hydrogen bonds occur with water molecules to form a stable solvation structure.

8. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to any one of claims 1 to 7, characterized in that: The VASP calculation program was used, and the geometric structure optimization parameters were: the generalized gradient approximation functional was used to approximate the exchange correlation potential, and different crystal models were optimized to an energy difference and force difference of less than 1×10 -5 eV / atom and 0.03eV / Å, with a cutoff energy of 600eV.

9. A method for predicting the difference in initial carbonation reaction of different crystalline C2S according to claim 8, characterized in that: The CHGCAR, AECCAR0 and AECCAR2 files obtained after VASP calculation are post-processed to obtain the charge files.

Images