Double Lattice Potential For Molecular Dynamics Simulation Of Silicon And Carbon

Carbon and silicon are important materials in the electronics industry and semiconductor industry.There are many interaction potentials for silicon and carbon in molecular dynamics.These potentials can accurately simulate the properties of materials in different aspects,but have many deficiencies in the simulation of the crystal structure of silicon and carbon.In order to reproduce the diamond structure of silicon and carbon,double lattice（DL）potential model is applied for molecular dynamics simulations.DL potential combines the Lennard-Jones potential into two fcc lattices and one atomic interaction potential between two lattices,to describe the crystal structure of stimulation system.In this dissertation,the DL potential is used in the molecular dynamics simulation of the crystal structure of silicon and carbon,and the crystal lattice of simulated system is identified by calculating the distribution functions of the distances between the atoms and the angles between the lines linking an atom with its nearest neighbors.For the validity test of MD simulation,the Tersoff potential,the Stillinger and Weber（SW）potential,the Environment-Dependent Interatomic potential（EDIP）,the Charge Optimized Many-Body（COMB）potential,and the Modified Embedded-Atom Method（MEAM）potential are also simulated for comparison.The crystal lattice,the crystallization temperature,and elastic constants have been calculated from MD simulations using above potentials.The results show that only the DL potential gives diamond lattice,and the physical parameters obtained from the simulation with DL potential are in agreement with the experiment results.The factors affecting the crystal structure of the simulation system are studied by changing the DL potential parameters.The results show that the system based on DL potential can obtain diamond structure when the cooling rate is fast,and lead-zinc structure can be obtained when the cooling rate is slow.By changing the ratio（σ_u）of the distance parameters（The shortest distance between atoms）in the DL potential,Cs Cl,Na Cl,ABO₃ and graphite structure can be obtained,andα-graphite andβ-graphite can be obtained by changing the simulation time and cut-off distance respectively.The thermal conductivity of diamond structures of silicon and carbon are calculated by non-equilibrium molecular dynamics and equilibrium molecular dynamics with the DL potential applied.The results show that at 300 K,the thermal conductivity of the silicon nanowires simulated by the NEMD method is 58.40±4.80 W/（m K）,and for carbon nanowires is 400±200 W/（m K）.The thermal conductivity for silicon crystal by the EMD method is35.31±3.80 W/（m K）,and for carbon crystal is 746.20±212.32 W/（m K）.The experimental results of thermal conductivity for silicon and carbon crystals at 300 K are 156 W/（m K）and2200 W/（m K）,respectively.This work shows the validity of DL potential for molecular dynamics simulation of silicon and carbon crystal structure.