Molecular aggregation information atomic scale calculation and analysis method of modified asphalt binder

Abstract

The invention discloses a molecular aggregation information atomic scale calculation and analysis method for a modified asphalt binder. The method comprises the following steps: generating a modified asphalt binder molecular model of a one-dimensional nano additive phase; performing energy minimization and structural relaxation on the model; calculating a space axis section of the one-dimensional nano additive phase; a corresponding mapping phase axis is obtained in a three-dimensional space according to periodic boundary conditions, and the shortest distance between axis sections is calculated; and calculating the distance between the atoms of different asphalt binder components and the axis section of the one-dimensional nano additive phase to obtain aggregation information of different molecules at the interface. According to the method, molecular modeling, molecular dynamics simulation and molecular aggregation information analysis are integrated, so that the molecular aggregation condition around the one-dimensional nano additive phase in the modified asphalt binder can be effectively analyzed from the atomic scale, and a theoretical basis is provided for regulation and control of physical / chemical characteristics of the modified asphalt binder; and reference is provided for atomic scale analytic calculation of microstructure evolution characteristics.

Description

Technical Field

[0001] The invention relates to the field of nano material molecular modeling and atomic scale simulation, and in particular to an atomic scale calculation and analysis method for molecular aggregation information of a modified asphalt binder. Background Art

[0002] Asphalt binder is a typical polymer material, and its road performance depends on the components and the proportion of the components. In order to regulate the mechanical and rheological properties of asphalt binders, different additive phases have been used in engineering and experimental research in recent years, especially nanomaterial additive phases, such as two-dimensional materials graphene oxide and one-dimensional carbon nanotubes. The addition of nano additive phases has a significant effect on the movement of asphalt component molecules. In actual engineering, the nano additive phase is mixed into the asphalt binder by stirring, and it is difficult to control its microscopic distribution, and it is easy to aggregate, which makes it difficult to effectively regulate the performance of the asphalt binder. At the same time, the microscopic configuration of the modified asphalt binder is difficult to effectively characterize during the experiment, which makes it difficult for us to grasp the microscopic regulation mechanism. Therefore, studying the microscopic characteristics of asphalt components and nano additive phases has important theoretical guiding significance for the regulation and prediction of asphalt binder performance.

[0003] Atomic-scale simulation can analyze the molecular aggregation and motion characteristics of modified asphalt binders and is currently widely used in the research and development of advanced nanomaterials. However, for the complex molecular system of asphalt binders, there is currently a lack of effective methods for analyzing the microstructure evolution, especially the aggregation information of molecules. Therefore, it is necessary to establish a calculation method for the aggregation information of nano-additive phases and molecules at the interface. Summary of the invention

[0004] In order to solve the problem that it is impossible to analyze the molecular aggregation information of existing modified asphalt binders experimentally, the present invention calculates the aggregation of asphalt binder molecules at the one-dimensional nano-additive phase interface through standardized molecular modeling, atomic scale simulation, and data analysis processes, thereby providing microstructural evolution characteristics that are difficult to obtain experimentally.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for atomic scale computational analysis of molecular aggregation information of a modified asphalt binder comprises the following steps:

[0007] S1: Establish molecular models of each component of asphalt binder and one-dimensional nano-additive phase model respectively. Based on the random walk theory, establish the molecular model of modified asphalt binder according to the preset model size, molecular number ratio and density, or model size, molecular molar mass ratio and density, and convert it into the data format required by molecular dynamics simulation software;

[0008] S2: according to the modified asphalt binder molecular model obtained in step S1, a molecular dynamics simulation input file is established, and relevant simulation parameters are set, including energy minimization, temperature and ensemble of structural relaxation; through molecular dynamics simulation, energy minimization and structural relaxation calculations are performed on the modified asphalt binder molecular model in sequence to obtain model topology information that changes with time steps;

[0009] S3: Based on the model microstructure obtained by structural relaxation in step S2, read the topological information of the corresponding time step, and determine the axis segment coordinates of each one-dimensional nano-additive phase model;

[0010] S4: Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step S3, the axis segment coordinates of seven mapped one-dimensional nano-additive phase models corresponding to each nano-additive are obtained according to the spatial information, and the minimum distance between two of the one-dimensional nano-additive phase models is calculated to obtain the axis segment spacing distribution information;

[0011] S5: Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step S4, the asphalt molecules are classified by components, and the distances from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-added phase model are calculated, so as to obtain the corresponding number of atoms and molecules according to the fixed cutoff distance.

[0012] Furthermore, the characteristic size of the one-dimensional nano-added phase model is smaller than 1 / 2 of the characteristic size of the modified asphalt binder molecular model, and the modified asphalt binder molecular model is a cube.

[0013] Furthermore, the step S1 includes the following sub-steps:

[0014] S11: Select a four-component model of asphalt, create a molecular model of each component, and simultaneously create a one-dimensional nano-additive phase model, and number the unit cells of the one-dimensional nano-additive phase model in sequence along the length direction of the one-dimensional nano-additive phase model;

[0015] S12: creating an initial model of the asphalt binder as a cubic periodic unit, setting the initial density of the asphalt binder, first adding multiple one-dimensional diamond models to the periodic unit, and numbering each one-dimensional diamond model, and numbering the carbon and hydrogen atoms in each one-dimensional diamond model; then filling the asphalt binder molecules into the periodic unit according to the initial density of the asphalt binder, and obtaining a modified asphalt binder molecular model;

[0016] S13: Convert the model file finally obtained in S12 into the data format required by the molecular dynamics simulation software.

[0017] Furthermore, the step S2 includes the following sub-steps:

[0018] S21: Based on the modified asphalt binder molecular model, a molecular dynamics simulation input file is created, and the energy minimization calculation of the modified asphalt binder molecular model is performed using a conjugate gradient algorithm to obtain a model restart file after energy minimization;

[0019] S22: Based on the model restart file after the energy minimization, a structure relaxation input file is created, and the canonical ensemble is used to perform equilibrium simulation on the modified asphalt binder molecular model, and the temperature is controlled to be 300K; on this basis, the isothermal and isobaric ensemble is used to perform equilibrium simulation on the modified asphalt binder molecular model, and the pressure is controlled to be 1atm and the temperature to be 300K to obtain the topological file of structure relaxation.

[0020] Furthermore, the step S3 includes the following sub-steps:

[0021] S31: Read the topological information of any time step according to the topological file of the structural relaxation outputted by S2, and determine the atomic coordinates of each one-dimensional nano-additive phase model according to the atomic number and molecular number information of the modified asphalt binder molecular model in step S1;

[0022] S32: Along the axial direction of the one-dimensional nano-added phase model, the unit cells are layered according to the atomic coordinates of each one-dimensional nano-added phase model, the periodicity of the modified asphalt binder molecular model is considered, the central coordinates of each unit cell are calculated, and the information of the axis segment of the entire one-dimensional nano-added phase model is obtained by interpolation.

[0023] Furthermore, the S4 comprises the following sub-steps:

[0024] S41: Based on the spatial geometric relationship of the periodic unit, each one-dimensional nano-additive phase model has seven corresponding mapping phases in space. According to the axis segment information of each one-dimensional nano-additive phase model, the seven mapping phase axis segment information of each one-dimensional nano-additive phase model is calculated and stored in the corresponding matrix;

[0025] S42: Calculate the minimum distance between two one-dimensional nano-added phase models, and then obtain the distribution and aggregation information of the one-dimensional nano-added phase.

[0026] Furthermore, the S5 comprises the following sub-steps:

[0027] S51: Based on the axis segment information of all one-dimensional nano-added phase models and the mapping phase, the distances from the atoms corresponding to all asphalt molecules to the axis segments are calculated; the one-dimensional nano-added phase model is approximated as a cylinder, and according to the set cutoff radius, the asphalt atom aggregation information at the interface of the one-dimensional nano-added phase model is obtained;

[0028] S52: Based on the asphalt atomic aggregation information and the asphalt binder molecular information of the modified asphalt binder molecular model, the aggregation information of various types of asphalt binder molecules is determined, so as to obtain the change of asphalt binder molecular aggregation at the interface over time by calculating the model topology at different time steps.

[0029] Furthermore, the one-dimensional nano-added phase model is a one-dimensional nano-diamond model.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) The present invention adopts molecular dynamics simulation technology to establish a molecular model of modified asphalt binder at the atomic scale, and studies the aggregation of one-dimensional nano-additive phase and molecules at the interface of asphalt binder, thus enriching the atomic scale simulation and analysis methods of the physical properties of modified asphalt binder.

[0032] (2) The present invention integrates microstructure modeling, simulation and data analysis to effectively analyze the evolution characteristics of the microstructure at the atomic scale, overcome the difficulties in experimental characterization of microstructure evolution, and provide a reference for the regulation of the physical properties of modified asphalt binders.

[0033] (3) The analytical method of the present invention is also applicable to other polymer material systems and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of an atomic-scale computational analysis method for molecular aggregation information of a modified asphalt binder according to an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of numbering of one-dimensional nanodiamonds along the length direction according to an embodiment of the present invention.

[0036] Figure 3 Schematic diagram of a modified asphalt binder molecular model generated according to an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of a one-dimensional nanometer added phase axis segment and a space mapping axis segment obtained in an embodiment of the present invention.

[0038] Figure 5 Schematic diagram of the spatial distance distribution of one-dimensional nano-addition phase axis segments according to an embodiment of the present invention.

[0039] Figure 6 A schematic diagram of a cumulative distribution function of a one-dimensional nanometer phase axis segment distance according to an embodiment of the present invention.

[0040] Figure 7 This is a schematic diagram of the change trend of the atomic number of the interface asphalt component over time in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] like Figure 1 As shown, the atomic scale computational analysis method for molecular aggregation information of the modified asphalt binder according to an embodiment of the present invention is divided into three parts: creation of molecular model, molecular dynamics simulation and molecular aggregation information analysis and calculation.

[0043] Step 1: Establishing the molecular model of modified asphalt binder

[0044] The molecular model of each component of the asphalt binder and the one-dimensional nano-additive phase model are established respectively. Based on the random walk theory, the molecular model of the modified asphalt binder is established according to the preset model size, molecular number ratio and density, or model size, molecular molar mass ratio and density, and converted into the data format required by the molecular dynamics simulation software. The molecular model of the asphalt binder component can contain any type of molecules, and the same type of molecules are classified when modeling; the nano-additive phase is a one-dimensional nanomaterial, whose characteristic size is less than 1 / 2 of the model characteristic size, and the model is set as a cube.

[0045] Step 1 specifically includes the following sub-steps:

[0046] S11: In this embodiment, a four-component model of asphalt binder is selected, and the four components correspond to four molecules, including asphaltene molecules (C 53 H 55 NOS), polar aromatic molecules (C 18 H 10 S2), saturated hydrocarbon molecules (C 22 H 46 ) and cycloalkane aromatic molecules (C 12 H 12 ). Build the molecular model of each component in Material Studio software or Avogadro software and save it as a .pdb file; at the same time, create a one-dimensional nanodiamond as a one-dimensional nano-additive phase model based on Matlab or Vesta software, and number the unit cells in sequence along the length direction. The characteristic size of the nano-additive phase model is selected as Save as a .pdb file.

[0047] S12: Create an initial model of the asphalt binder as a cubic periodic unit, set the initial density of the asphalt binder, first add multiple one-dimensional diamond models to the periodic unit, and number each one-dimensional diamond model, and number the carbon and hydrogen atoms in each one-dimensional diamond model; then fill the asphalt binder molecules into the periodic unit according to the initial density of the asphalt binder to obtain a modified asphalt binder molecular model. In this embodiment, the model can be packaged and modeled through the Amorphous Cell module in Material Studio, or after modeling through the Packmol package, the model is saved as .car and .mdf files. In this embodiment, the periodic unit is Initial density of asphalt binder 1.05 g cm -3 There are 12 one-dimensional diamond models added, so they are numbered 1-12. At the same time, the carbon and hydrogen atoms in each one-dimensional diamond model are numbered, such as Figure 2 The molecular model of modified asphalt binder is shown in Figure 3 shown.

[0048] S13: Convert the model file finally obtained in S12 into the data format required by the molecular dynamics simulation software. In this embodiment, the model file is converted into the molecular dynamics simulation data topology format by using the msi2lmp toolkit provided by the open source software LAMMPS.

[0049] Step 2: Energy minimization and structural relaxation of the modified asphalt binder molecular model

[0050] According to the modified asphalt binder molecular model obtained in step one, a molecular dynamics simulation input file is established, and relevant simulation parameters are set, including energy minimization, temperature and ensemble of structural relaxation; through molecular dynamics simulation, the modified asphalt binder molecular model is subjected to energy minimization and structural relaxation calculations in turn to obtain the model topology information that changes with time steps.

[0051] S21: This embodiment is based on the open source software LAMMPS to create a molecular dynamics simulation .inp input file, and uses the conjugate gradient (CG) algorithm to perform energy minimization calculations on the modified asphalt binder molecular model to obtain a model restart file after energy minimization;

[0052] S22: Based on the model restart file after energy minimization, create a structural relaxation .inp input file, use the canonical ensemble to simulate the equilibrium state of the modified asphalt binder molecular model, and control the temperature to 300K; on this basis, use the isothermal and isobaric ensemble to simulate the equilibrium state of the model, control the pressure to 1atm and the temperature to 300K, and obtain the topological file of structural relaxation.

[0053] Step 3: Axis calculation of one-dimensional nano-additive phase model

[0054] Based on the model microstructure obtained by structural relaxation in step 2, read the topological information of the corresponding time step and determine the axis segment coordinates of each one-dimensional nano-additive phase model. Specifically include:

[0055] S31: Read the topological information of any time step according to the topological file of the structural relaxation outputted in step 2, and determine the atomic coordinates of each one-dimensional nano-additive phase model according to the atomic number and molecular number information of the modified asphalt binder molecular model in step S1. The information reading of this embodiment is realized by Matlab programming, but it can also be realized by C, python and other programming.

[0056] S32: Along the axis of the one-dimensional nano-added phase model, according to the atomic coordinates of each one-dimensional nano-added phase model, the unit cell is layered, the periodicity of the modified asphalt binder molecular model is considered, the central coordinates of each unit cell are calculated, and the information of the axis segment of the entire one-dimensional nano-added phase model is obtained by interpolation. The results are as follows: Figure 4 shown.

[0057] Step 4: One-dimensional nano-additive phase model mapping axis and spacing calculation

[0058] Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step 3, the axis segment coordinates of the seven mapped one-dimensional nano-additive phase models corresponding to each nano-additive are obtained according to the spatial information, and the minimum distance between the one-dimensional nano-additive phase models is calculated to obtain the axis segment spacing distribution information, which specifically includes the following sub-steps:

[0059] S41: Based on the spatial geometric relationship of the periodic unit, each one-dimensional nano-added phase model has seven corresponding mapping phases in space. According to the axis segment information of each one-dimensional nano-added phase model, the seven mapping phase axis segment information of each one-dimensional nano-added phase model is calculated and stored in the corresponding matrix.

[0060] S42: Calculate the minimum distance between the one-dimensional nano-additive phase models, and then obtain the distribution and aggregation information of the one-dimensional nano-additive phase. The result is as follows: Figure 5 and 6 As shown. Figure 5 and 6 It can be seen that the minimum distance distribution of the one-dimensional nano-added phase.

[0061] In this embodiment, step 4 is implemented by Matlab programming, but can also be implemented by C, Python and other programming.

[0062] Step 5: Calculation of aggregation information of molecules at the added phase interface

[0063] Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step 4, the asphalt molecules are classified by components, and the distances from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-added phase model are calculated, thereby obtaining the corresponding number of atoms and molecules according to the fixed cutoff distance. Step 5 specifically includes the following sub-steps:

[0064] S51: Based on the axis segment information of all one-dimensional nano-added phase models and the mapping phase, the distances from the atoms corresponding to all asphalt molecules to the axis segments are calculated; the one-dimensional nano-added phase model is approximated as a cylinder, and according to the set cutoff radius, the asphalt atom aggregation information at the interface of the one-dimensional nano-added phase model is obtained;

[0065] S52: Based on the asphalt atomic aggregation information and the asphalt binder molecular information of the modified asphalt binder molecular model, the aggregation information of various types of asphalt binder molecules is determined, so as to obtain the change of asphalt binder molecular aggregation at the interface over time by calculating the model topology at different time steps.

[0066] In this embodiment, the cutoff radius is 0.25 nm, and the calculation of the aggregation information of the molecules at the added phase interface in step 5 is implemented by Matlab programming, but can also be implemented by C, Python, etc. The change of molecular aggregation at the interface finally obtained in this embodiment over time is shown in Figure 7 As shown. Figure 7 It can be seen that, compared with the other three types of molecules, saturated hydrocarbon molecules aggregate most at the interface of the one-dimensional nano-additive phase model.

[0067] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A method for atomic scale computational analysis of molecular aggregation information of modified asphalt binder, characterized in that: The steps include: S1: Establish molecular models of each component of asphalt binder and one-dimensional nano-additive phase model respectively. Based on the random walk theory, establish the molecular model of modified asphalt binder according to the preset model size, molecular number ratio and density, or model size, molecular molar mass ratio and density, and convert it into the data format required by molecular dynamics simulation software; S2: according to the modified asphalt binder molecular model obtained in step S1, a molecular dynamics simulation input file is established, and relevant simulation parameters are set, including energy minimization, temperature and ensemble of structural relaxation; through molecular dynamics simulation, energy minimization and structural relaxation calculations are performed on the modified asphalt binder molecular model in sequence to obtain model topology information that changes with time steps; S3: Based on the model microstructure obtained by structural relaxation in step S2, read the topological information of the corresponding time step, and determine the axis segment coordinates of each one-dimensional nano-additive phase model; S4: Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step S3, the axis segment coordinates of seven mapped one-dimensional nano-additive phase models corresponding to each nano-additive are obtained according to the spatial information, and the minimum distance between two of the one-dimensional nano-additive phase models is calculated to obtain the axis segment spacing distribution information; S5: Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step S4, the asphalt molecules are classified by components, and the distances from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-added phase model are calculated, so as to obtain the corresponding number of atoms and molecules according to the fixed cutoff distance.

2. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 1, characterized in that: The characteristic size of the one-dimensional nano-additive phase model is smaller than 1 / 2 of the characteristic size of the modified asphalt binder molecular model, and the modified asphalt binder molecular model is a cube.

3. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 1, characterized in that: The step S1 includes the following sub-steps: S11: Select a four-component model of asphalt, create a molecular model of each component, and simultaneously create a one-dimensional nano-additive phase model, and number the unit cells of the one-dimensional nano-additive phase model in sequence along the length direction of the one-dimensional nano-additive phase model; S12: creating an initial model of the asphalt binder as a cubic periodic unit, setting the initial density of the asphalt binder, first adding multiple one-dimensional diamond models to the periodic unit, and numbering each one-dimensional diamond model, and numbering the carbon and hydrogen atoms in each one-dimensional diamond model; then filling the asphalt binder molecules into the periodic unit according to the initial density of the asphalt binder, and obtaining a modified asphalt binder molecular model; S13: Convert the model file finally obtained in S12 into the data format required by the molecular dynamics simulation software.

4. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 3 is characterized in that: The step S2 includes the following sub-steps: S21: Based on the modified asphalt binder molecular model, a molecular dynamics simulation input file is created, and the energy minimization calculation of the modified asphalt binder molecular model is performed using a conjugate gradient algorithm to obtain a model restart file after energy minimization; S22: Based on the model restart file after the energy minimization, a structure relaxation input file is created, and the canonical ensemble is used to perform equilibrium simulation on the modified asphalt binder molecular model, and the temperature is controlled to be 300K; on this basis, the isothermal and isobaric ensemble is used to perform equilibrium simulation on the modified asphalt binder molecular model, and the pressure is controlled to be 1atm and the temperature to be 300K to obtain the topological file of structure relaxation.

5. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 4, characterized in that: The step S3 includes the following sub-steps: S31: Read the topological information of any time step according to the topological file of the structural relaxation outputted by S2, and determine the atomic coordinates of each one-dimensional nano-additive phase model according to the atomic number and molecular number information of the modified asphalt binder molecular model in step S1; S32: Along the axial direction of the one-dimensional nano-added phase model, the unit cells are layered according to the atomic coordinates of each one-dimensional nano-added phase model, the periodicity of the modified asphalt binder molecular model is considered, the central coordinates of each unit cell are calculated, and the information of the axis segment of the entire one-dimensional nano-added phase model is obtained by interpolation.

6. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 5, characterized in that: The S4 comprises the following sub-steps: S41: Based on the spatial geometric relationship of the periodic unit, each one-dimensional nano-additive phase model has seven corresponding mapping phases in space. According to the axis segment information of each one-dimensional nano-additive phase model, the seven mapping phase axis segment information of each one-dimensional nano-additive phase model is calculated and stored in the corresponding matrix; S42: Calculate the minimum distance between two one-dimensional nano-added phase models, and then obtain the distribution and aggregation information of the one-dimensional nano-added phase.

7. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 6, characterized in that: The S5 comprises the following sub-steps: S51: Based on the axis segment information of all one-dimensional nano-added phase models and the mapping phase, the distances from the atoms corresponding to all asphalt molecules to the axis segments are calculated; the one-dimensional nano-added phase model is approximated as a cylinder, and according to the set cutoff radius, the asphalt atom aggregation information at the interface of the one-dimensional nano-added phase model is obtained; S52: Based on the asphalt atomic aggregation information and the asphalt binder molecular information of the modified asphalt binder molecular model, the aggregation information of various types of asphalt binder molecules is determined, so as to obtain the change of asphalt binder molecular aggregation at the interface over time by calculating the model topology at different time steps.

8. The atomic scale computational analysis method for molecular aggregation information of modified asphalt binder according to claim 1, characterized in that: The one-dimensional nano-added phase model is a one-dimensional nano-diamond model.

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