## 1 Introduction
### Molecular Dynamics (MD) Method  
Molecular Dynamics (MD), originating in theoretical physics, was applied widely in materials science [13; 14]. MD is a kind of computer program to simulate the movements of atoms in materials, and the atoms and molecules interact for a designated time based on the [PERSON]'s law of motion. The trajectories of atoms and molecules are monitored, and the energy of the system is computed. In physics, MD was used to examine physical properties [13; 14]. The evolution of dynamics in a single molecule is used to determine the macro properties of the system. The \"statistical mechanics by number\" and \"[PERSON]'s vision of Newtonian mechanics\" were also used to describe the molecular dynamics. The simulation size and total duration were selected so that the calculation can be finished within a reasonable amount of time [15]. The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [16] and the Monte Carlo for Complex Chemical Systems (MCCCS) program [17] were commonly used for MD simulations. The computation algorithm of the MD simulation is shown in Figure 1. In addition, compared to other methods (such as Finite Element Method (FEM) and Discrete Element Method (DEM)), the MD method helps address specific problems or principles of atoms or materials, and also, a specific property can be studied by altering specific contributions. Moreover, the material behaviors or response can be analyzed under extreme conditions on a nanoscale. Recently, three components of mixtures (asphaltenes, aromatics and saturates) were chosen to represent the asphalt using MD simulation. In this reference model, 1,7-dimethylnaphthalene (C\({}_{12}\)H\({}_{12}\)) and docosane (n-C\({}_{22}\)H\({}_{46}\)) were represented as naphthene aromatics and saturates, respectively [18]. Two kinds of asphaltene structures were used, and the density of each component was calculated using the MD method. From the simulation results, there are still many differences between the test and the simulation data in the calculations of the glass transition temperature and bulk modulus [18]. A new asphalt model with four components (asphaltenes, polar aromatics, naphthene aromatics and saturates) was created, and the density and thermal expansion coefficient of the asphalt model were calculated. The MD simulation results agreed with the laboratory data [19]. In addition, polystyrene was added to this asphalt model for polymer modification analysis. The radial distribution functions g(r) of components of the asphalt model were computed [19]. The MD simulation was also recently applied to study the self-diffusivity properties of asphalt binders. The effect of healing on the fatigue performance of binders was studied, and the MD model of an asphalt binder was created to predict the healing effect. The self-diffusion effect caused the binder molecules to flow across the crack interface. The correlation between the length and branching of molecules and self-diffusion of asphalt molecules was investigated [20]. The relationship between the asphalt and aggregate was established and the asphalt-quartz structure model of the interface was used in the system. The Consistent-Valence Force Field (CVFF_aug) was considered in this simulation to characterize the inter-atom interactions [21]. Based on a literature review, few researchers used MD to simulate modified asphalt and studied the physical properties of modified asphalt models in engineering disciplines. Graphite has a high thermal stability, high electrical conductivity, good self-lubricating and dry lubricating properties. The graphite was used to modify asphalt binder, and thermal conductivity and anti-aging properties improved after the addition of graphite in the asphalt binder [22; 23]. Due to these improvements, in this study, the common multi-layer graphite model was adopted, and the components of the control asphalt model was composed of asphaltenes, saturates and aromatics.