Qili Zhang
Institute of Applied Physics and Computational Mathematics, China
Title: The thermodynamic and optical properties of diamond: A first-principles study
Biography
Biography: Qili Zhang
Abstract
The T=300 K isotherm of diamond is calculated by using density-functional molecular dynamics. The results show that the PAW-PBE potential is more close to the experimental data. The thermodynamic states accessible under shock conditions are given by the principal Hugoniot which satisfying the Rankine-Hugoniot equations, the internal energy and pressure at a given density and temperature are calculated by using density-functional molecular dynamics, the initial state was taken to be un-shocked diamond with ρ0=3.475 g/cm3, T=300 K, and P0≈0GPa, which obtained from the T=300 K isotherm. Our principal Hugoniot is similar with the result of Nichols in the literature, but is little higher in pressure and temperature, the solid-liquid coexistence region is from ρ=6.0 g/cm3 to 6.95 g/cm3. Knowledge of the sound velocity is essential for a variety of research areas; moreover, the pressure and temperature dependence of the sound velocity can be used to constrain the equation of state. This work presents two theory methods to calculate the sound velocity of solid phase along the principal Hugoniot: One by using the Gruneisen equation state and the isotherm at T=300 K, the other by using the specific heat, the pressure derivative with respect to the density and to the temperature along the principle Hugoniot, the results are consistent with each other. The optical reflectivity of the diamond on the principal Hugoniot is also calculated, the result is consistent with the experimental results in the literature.