Effect Of Vacancy Concentration On Elastic Property In Aluminum Under High Pressures

In reality, it is difficult to find perfect metallic crystals, where all atoms are arranged in periodical lattice. More or less, various defects exist in real metals. These defects can seriously affect the properties of metals. Among them, point defect is an important kind of lattice defects. Through their generation, motion, and interaction, the point defects will aggregate or disappear in metals, especially play an important role to affect plasticity, strength, diffusion and structural sensitive properties of metals. This field has attracted attention of many scientists and amount of theoretic and experimental works have been done. In terms of methodology, molecular dynamics (MD) simulation has been widely used due to the advantage to easily describe the properties of defects at atomistic scale. But there has no report about how point defects affect the elastic properties of metals under different pressure so far.In this thesis, the effect of vacancy concentration on elastic properties of aluminum under high pressures (from–15 GPa to 20 GPa) is studied by means of MD simulation. The embedded-atom model (EAM) is employed to describe inter-atomic interaction in face-centered cubic (FCC) aluminum. In order to avoid the influence of surface effect, the periodic boundary conditions is employed in simulation, so that the defect can move in the infinite space. To control the constant temperature and stress, Nosé-Hoover method and Parrinello-Rahman method are used, respectively. The main contents of the investigation are listed as follows:1. MD method with EAM potential were used to study the elastic constants under pressures ranging from -15GPa to 20GPa in the cell with size of 32.404?×32.404?×32.404?. The linear relation between the elastic constants and pressure was obtained. The data were fitted to Murnagahan isothermal equation of state (EOS) to get the bulk modulus. The P-V/V0 relation is compared with experimental result and we determined the pressure range where the EAM potential is valid.