Method for analyzing molecular aggregation information of modified asphalt binder at atomic scale

Abstract

The application discloses a method for calculating and analyzing molecular aggregation information of modified asphalt binder, generates a one-dimensional nanometer additive phase modified asphalt binder molecular model, performs energy minimization and structure relaxation on the model, calculates a one-dimensional nanometer additive phase space axis segment, obtains a corresponding mapping phase axis according to a period boundary condition in three-dimensional space, and calculates the shortest distance between the axis segments, calculates the distance between different asphalt binder component atoms and the one-dimensional nanometer additive phase axis segment, and obtains the aggregation information of different molecules at the interface. The application integrates molecular modeling, molecular dynamics simulation and molecular aggregation information analysis, can effectively analyze the molecular aggregation around the one-dimensional nanometer additive phase in the modified asphalt binder from the atomic scale, provides a theoretical basis for the regulation of the physical / chemical characteristics of the modified asphalt binder, and provides a reference for the atomic scale analysis and calculation of the microstructure evolution characteristics.

Description

Technical Field

[0001] This invention relates to the field of molecular modeling and atomic-scale simulation of nanomaterials, and in particular to a method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binders. Background Technology

[0002] Asphalt binders are typical polymer materials, and their road performance depends on their components and their proportions. In recent years, to regulate the mechanical and rheological properties of asphalt binders, different additive phases, especially nanomaterials such as two-dimensional graphene oxide and one-dimensional carbon nanotubes, have been used in engineering and experimental research. The addition of nanomaterials significantly affects the movement of asphalt component molecules. In practical engineering, the microstructure of nanomaterials is difficult to control when mixed into asphalt binders, and they are prone to aggregation, making it difficult to effectively regulate the performance of asphalt binders. Furthermore, the microstructure of modified asphalt binders is difficult to characterize effectively during experiments, making it difficult to grasp the micro-regulation mechanism. Therefore, studying the microscopic characteristics of asphalt components and nanomaterials is of significant theoretical guiding importance for the regulation and prediction of asphalt binder performance.

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

[0004] To address the problem that existing experiments on modified asphalt binders cannot analyze molecular aggregation information, this invention uses standardized molecular modeling, atomic-scale simulation, and data analysis processes to calculate the aggregation of asphalt binder molecules at the one-dimensional nano-additive phase interface, thereby providing microstructural evolution characteristics that are difficult to obtain experimentally.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binders, comprising the following steps:

[0007] S1: Establish molecular models and one-dimensional nano-additive phase models for each component of the asphalt binder. Based on the random walk theory, establish molecular models of the 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 them into the data format required by the molecular dynamics simulation software.

[0008] S2: Based on the modified asphalt binder molecular model obtained in step S1, establish a molecular dynamics simulation input file, set relevant simulation parameters, including energy minimization, structural relaxation temperature, and ensemble; perform energy minimization and structural relaxation calculations on the modified asphalt binder molecular model sequentially through molecular dynamics simulation to obtain model topology information that changes with time step;

[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 coordinates of the axis segment of each one-dimensional nano-added phase model.

[0010] S4: Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step S3, obtain the axis segment coordinates of the seven mapped one-dimensional nano-added phase models corresponding to each nano-added phase according to the spatial information, and calculate the minimum distance between each pair of one-dimensional nano-added phase models to obtain the axis segment spacing distribution information.

[0011] S5: Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step S4, classify the asphalt molecules according to their components, calculate the distance from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-additive phase model, and thus obtain the corresponding number of atoms and molecules according to the fixed cutoff distance.

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

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

[0014] S11: Select the four-component model of asphalt, create the molecular model of each component, and at the same time create a one-dimensional nano-additive phase model. Then, 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: The initial model of the asphalt binder is a periodic cubic unit. The initial density of the asphalt binder is set. First, multiple one-dimensional diamond models are added to the periodic unit, and each one-dimensional diamond model is numbered, as are the carbon and hydrogen atoms in each one-dimensional diamond model. Then, according to the initial density of the asphalt binder, asphalt binder molecules are filled into the periodic unit to obtain the modified asphalt binder molecular model.

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

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

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

[0019] S22: Based on the model restart file after energy minimization, create a structural relaxation input file, and use a regular ensemble to perform an equilibrium simulation of the modified asphalt binder molecular model, controlling the temperature at 300K; on this basis, use an isothermal and isobaric ensemble to perform an equilibrium simulation of the modified asphalt binder molecular model, controlling the pressure at 1 atm and the temperature at 300K, to obtain the topology file of structural relaxation.

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

[0021] S31: Based on the topology file of structural relaxation output by S2, read the topology information at any time step, 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 axis of the one-dimensional nano-additive phase model, based on the atomic coordinates of each one-dimensional nano-additive phase model, the unit cell is divided into layers. Considering the periodicity of the modified asphalt binder molecular model, the center coordinates of each unit cell are calculated, and the information of the axis segment of the entire one-dimensional nano-additive phase model is obtained by interpolation.

[0023] Further, step S4 includes the following sub-steps:

[0024] S41: Based on the spatial geometric relationship of periodic units, 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, calculate the axis segment information of the seven mapping phases of each one-dimensional nano-added phase model and store it in the corresponding matrix.

[0025] S42: Calculate the minimum distance between each pair of the one-dimensional nano-added phase model to obtain the distribution and aggregation information of the one-dimensional nano-added phase.

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

[0027] S51: Based on the axis segment information of all one-dimensional nano-additive phase models and mapped phases, calculate the distance from the atoms corresponding to all asphalt molecules to the axis segment; approximate the one-dimensional nano-additive phase model as a cylinder, and obtain the asphalt atom aggregation information at the interface of the one-dimensional nano-additive phase model according to the set cutoff radius.

[0028] S52: Based on the information on the aggregation of asphalt atoms and the molecular information of the modified asphalt binder, the aggregation information of various asphalt binder molecules is determined. Then, by calculating the model topology at different time steps, the change of asphalt binder molecule aggregation at the interface over time is obtained.

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

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

[0031] (1) This invention uses 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 phases and molecules of asphalt binder at the interface, thus enriching the atomic-scale simulation analysis methods for the physical properties of modified asphalt binder.

[0032] (2) This invention integrates microstructure modeling, simulation and data analysis, which can effectively analyze the evolution characteristics of microstructure at the atomic scale, overcome the difficulties in experimental microstructure evolution characterization, 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. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the atomic-scale calculation and analysis method for molecular aggregation information of modified asphalt binders according to an embodiment of the present invention.

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

[0036] Figure 3 This is a schematic diagram of the molecular model of the modified asphalt binder generated in an embodiment of the present invention.

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

[0038] Figure 5 This is a schematic diagram of the spatial distance distribution of the one-dimensional nano-added phase axis segments in an embodiment of the present invention.

[0039] Figure 6 This is a schematic diagram of the cumulative distribution function of the distance between the one-dimensional nano-added phase axis segments in an embodiment of the present invention.

[0040] Figure 7 This is a schematic diagram illustrating the trend of the number of atoms in the interfacial asphalt component over time, according to an embodiment of the present invention. Detailed Implementation

[0041] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

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

[0043] Step 1: Establishing a molecular model for modified asphalt binders

[0044] Molecular models and one-dimensional nano-additive phase models of each component of the asphalt binder were established separately. Based on the random walk theory, molecular models of the modified asphalt binder were built according to 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 models of the asphalt binder components can contain any type of molecule, and molecules of the same type are classified during modeling. The nano-additive phase is a one-dimensional nanomaterial, and its characteristic size must be less than 1 / 2 of the model's characteristic size; the model is set as a cube.

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

[0046] S11: In this embodiment, a four-component model of asphalt binder is selected. The four components correspond to four types of 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 cycloalkanes (C 12 H 12 In Material Studio or Avogadro software, construct molecular models of each component and save them as .pdb files. Simultaneously, create a one-dimensional nanodiamond model as a one-dimensional nano-additive phase model using Matlab or Vesta software, and number the unit cells sequentially along the length direction. The characteristic size of the nano-additive phase model is selected as... Save it as a .pdb file.

[0047] S12: The initial model of the asphalt binder is created as a periodic cell of cubes. The initial density of the asphalt binder is set. First, multiple one-dimensional diamond models are added to the periodic cell, and each one-dimensional diamond model is numbered, as are the carbon and hydrogen atoms within each one-dimensional diamond model. Then, based on the initial density of the asphalt binder, asphalt binder molecules are filled into the periodic cell to obtain a modified asphalt binder molecular model. In this embodiment, the model can be packaged and modeled using the Amorphous Cell module in Material Studio, or modeled using the Packmol package and then saved as .car and .mdf files. In this embodiment, the periodic cell is... The initial density of the asphalt binder is 1.05 g·cm³. -3 There are 12 one-dimensional diamond models in total, so they are numbered 1-12. The carbon and hydrogen atoms in each one-dimensional diamond model are also numbered, such as... Figure 2 As shown. The completed molecular model of the modified asphalt binder is as follows. Figure 3 As shown.

[0048] S13: Convert the model file 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 using the msi2lmp toolkit provided by the open-source software LAMMPS.

[0049] Step 2: Energy Minimization and Structural Relaxation of Molecular Model for Modified Asphalt Binder

[0050] Based on 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 for structural relaxation, and ensemble. Energy minimization and structural relaxation calculations are performed sequentially on the modified asphalt binder molecular model through molecular dynamics simulation to obtain the model topology information that changes with time step.

[0051] S21: This embodiment is based on the open-source software LAMMPS. A molecular dynamics simulation .inp input file is created, and the conjugate gradient (CG) algorithm is used to perform energy minimization calculations on the molecular model of the modified asphalt binder to obtain the 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 a regular ensemble to perform equilibrium simulation on the modified asphalt binder molecular model, and control the temperature at 300K; on this basis, use an isothermal and isobaric ensemble to perform equilibrium simulation on the model, and control the pressure at 1atm and the temperature at 300K to obtain the topology file of structural relaxation.

[0053] Step 3: Axis Calculation of the One-Dimensional Nanoparticle Additive Phase Model

[0054] Based on the model microstructure obtained from the structural relaxation in step two, the topological information of the corresponding time step is read to determine the coordinates of the axis segments of each one-dimensional nano-added phase model. Specifically, this includes:

[0055] S31: Based on the topology file of structural relaxation output in step two, read the topology information at any time step, and determine the atomic coordinates of each one-dimensional nano-additive phase model according to the atomic and molecular indices of the modified asphalt binder molecular model described in step S1. In this embodiment, information reading is implemented through Matlab programming, but it can also be implemented through programming languages ​​such as C and Python.

[0056] S32: Along the axis of the one-dimensional nano-additive phase model, based on the atomic coordinates of each one-dimensional nano-additive phase model, the unit cell is layered. Considering the periodicity of establishing the modified asphalt binder molecular model, the center coordinates of each unit cell are calculated. Information about the axial segment of the entire one-dimensional nano-additive phase model is obtained through interpolation. The results are as follows: Figure 4 As shown.

[0057] Step 4: Calculation of mapping axes and spacing for one-dimensional nano-added phase model

[0058] Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step three, the axis segment coordinates of the seven mapped one-dimensional nano-added phase models corresponding to each nano-added are obtained according to the spatial information. The minimum distance between each pair of one-dimensional nano-added phase models is calculated to obtain the axis segment spacing distribution information. The specific steps include the following:

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

[0060] S42: Calculate the minimum distance between each pair of the one-dimensional nano-added phase model to obtain the distribution and aggregation information of the one-dimensional nano-added phase. The results are as follows: Figure 5 and 6 As shown. From Figure 5 and 6 The minimum distance distribution of the one-dimensional nano-added phase can be observed.

[0061] In this embodiment, step four is implemented using Matlab programming, but it can also be implemented using programming languages ​​such as C and Python.

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

[0063] Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step four, asphalt molecules are classified according to their components. The distance from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-additive phase model is calculated, thereby obtaining the corresponding number of atoms and molecules according to a fixed cutoff distance. Step five specifically includes the following sub-steps:

[0064] S51: Based on the axis segment information of all one-dimensional nano-additive phase models and mapped phases, calculate the distance from the atoms corresponding to all asphalt molecules to the axis segment; approximate the one-dimensional nano-additive phase model as a cylinder, and obtain the asphalt atom aggregation information at the interface of the one-dimensional nano-additive phase model according to the set cutoff radius.

[0065] S52: Based on the information on the aggregation of asphalt atoms and the molecular information of the modified asphalt binder, the aggregation information of various asphalt binder molecules is determined. Then, by calculating the model topology at different time steps, the change of asphalt binder molecule aggregation at the interface over time is obtained.

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

[0067] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binders, characterized in that, Includes the following steps: S1: Establish molecular models and one-dimensional nano-additive phase models for each component of the asphalt binder. Based on the random walk theory, establish molecular models of the 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 them into the data format required by the molecular dynamics simulation software. S2: Based on the modified asphalt binder molecular model obtained in step S1, establish a molecular dynamics simulation input file, set the relevant simulation parameters, including energy minimization, structural relaxation temperature and ensemble; perform energy minimization and structural relaxation calculations on the modified asphalt binder molecular model through molecular dynamics simulation to obtain the model topology information that changes with time step; 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 coordinates of the axis segment of each one-dimensional nano-added phase model. S4: Based on the axis segment coordinates of the one-dimensional nano-added phase model obtained in step S3, obtain the axis segment coordinates of the seven mapped one-dimensional nano-added phase models corresponding to each nano-added phase according to the spatial information, and calculate the minimum distance between each pair of one-dimensional nano-added phase models to obtain the axis segment spacing distribution information. S5: Based on the axis segment coordinates of the one-dimensional nano-additive phase model obtained in step S4, classify the asphalt molecules according to their components, calculate the distance from the atoms corresponding to all asphalt molecules to the axis segment of the one-dimensional nano-additive phase model, and thus obtain the corresponding number of atoms and molecules according to the fixed cutoff distance.

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

3. The method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binder according to claim 1, characterized in that, Step S1 includes the following sub-steps: S11: Select the four-component model of asphalt, create the molecular model of each component, and at the same time create a one-dimensional nano-additive phase model. Then, 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: The initial model of the asphalt binder is a periodic cubic unit. The initial density of the asphalt binder is set. First, multiple one-dimensional diamond models are added to the periodic unit, and each one-dimensional diamond model is numbered, as are the carbon and hydrogen atoms in each one-dimensional diamond model. Then, according to the initial density of the asphalt binder, asphalt binder molecules are filled into the periodic unit to obtain the modified asphalt binder molecular model. S13: Convert the model file obtained in S12 into the data format required by the molecular dynamics simulation software.

4. The method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binder according to claim 3, characterized in that, Step S2 includes the following sub-steps: S21: Based on the molecular model of modified asphalt binder, create a molecular dynamics simulation input file, use the conjugate gradient algorithm to perform energy minimization calculation on the molecular model of modified asphalt binder, and obtain the model restart file after energy minimization; S22: Based on the model restart file after energy minimization, create a structural relaxation input file, and use a regular ensemble to perform an equilibrium simulation of the modified asphalt binder molecular model, controlling the temperature at 300K; on this basis, use an isothermal and isobaric ensemble to perform an equilibrium simulation of the modified asphalt binder molecular model, controlling the pressure at 1 atm and the temperature at 300K, to obtain the topology file of structural relaxation.

5. The method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binder according to claim 4, characterized in that, Step S3 includes the following sub-steps: S31: Based on the topology file of structural relaxation output by S2, read the topology information at any time step, 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 axis of the one-dimensional nano-additive phase model, based on the atomic coordinates of each one-dimensional nano-additive phase model, the unit cell is divided into layers. Considering the periodicity of the modified asphalt binder molecular model, the center coordinates of each unit cell are calculated, and the information of the axis segment of the entire one-dimensional nano-additive phase model is obtained by interpolation.

6. The method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binder according to claim 5, characterized in that, S4 includes the following sub-steps: S41: Based on the spatial geometric relationship of periodic units, 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, calculate the axis segment information of the seven mapping phases of each one-dimensional nano-added phase model and store it in the corresponding matrix. S42: Calculate the minimum distance between each pair of the one-dimensional nano-added phase model to obtain the distribution and aggregation information of the one-dimensional nano-added phase.

7. The method for atomic-scale calculation and analysis of molecular aggregation information of modified asphalt binder according to claim 6, characterized in that, S5 includes the following sub-steps: S51: Based on the axis segment information of all one-dimensional nano-additive phase models and mapped phases, calculate the distance from the atoms corresponding to all asphalt molecules to the axis segment; approximate the one-dimensional nano-additive phase model as a cylinder, and obtain the asphalt atom aggregation information at the interface of the one-dimensional nano-additive phase model according to the set cutoff radius. S52: Based on the information on the aggregation of asphalt atoms and the molecular information of the modified asphalt binder, the aggregation information of various asphalt binder molecules is determined. Then, by calculating the model topology at different time steps, the change of asphalt binder molecule aggregation at the interface over time is obtained.

8. The method for atomic-scale calculation and analysis of 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 nanodiamond model.

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