The effect of dislocations on the thermodynamic properties of Ta single crystal under high pressure by molecular dynamics simulation**Project supported by the National Natural Science Foundation of China (Grant No. 51231002) and the Basic Scientific Research Projects in Central Colleges and Universities (Grant No. 2018ZD10).

Abstract

The thermodynamic properties of Ta metal under high pressure are studied by molecular dynamics simulation. For dislocation-free Ta crystal, all the thermodynamic properties considered are in good agreement with the results from experiments or higher level calculations. If dislocations are included in the Ta crystal, it is found that as the dislocation density increases, the hydrostatic pressure at the phase transition point of bcc→hcp and hcp→fcc decreases, while the Hugoniot temperature increases. Meanwhile, the impact pressure at the elastic–plastic transition point is found to depend on the crystallographic orientation of the pressure. As the dislocation density increases, the pressure of the elastic–plastic transition point decreases rapidly at the initial stage, then gradually decreases with the increase of the dislocation density.