Improved embedded-atom model potentials of Pb at high pressure: application to investigations of plasticity and phase transition under extreme conditions

K Wang and WJ Zhu and MZ Xiang and Y Xu and GM Li and J Chen, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 27, 015001 (2019).

DOI: 10.1088/1361-651X/aaea55

Local stress relaxation mechanisms of crystals are a long-standing interest in the field of materials physics. Constantly encountered inelastic deformation mechanisms in metals under dynamic loadings, such as dislocation, deformation twinning and phase transition, have been extensively discussed separately or as some of their combinations. Recently, virtual melting is found to be a dominant local stress relaxation mechanism under extreme strain rates. However, these deformation mechanisms have never been investigated in the same metal at an atomic level due to the lack of high pressure interatomic potentials. In this work, an embedded-atom model potential of Pb is developed and tested for high pressure applications. The developed potential of Pb could not only reproduce many energetic, elastic and defective properties at ambient conditions well, but also correctly describe face- centered cubic (fcc)-hexagonal close packed (hcp) and hcp-body-centered cubic phase transition of Pb under high pressures. Shock Hugoniot, as well as equation of states for fcc and hcp phase, also agrees well with the literature ones up to more than 100 GPa. With the developed potential, non-equilibrium molecular dynamic simulations are conducted to investigate dynamic behaviors of Pb single crystal under ramp-shock compressions. Depending on applied strain rates, dislocationmediated plasticity, phase transition and virtual melting, constantly reported by experiments or theoretical investigations, are observed in our results. Additionally, a new phase transition mechanism of Pb subjected to the ramp compressions is uncovered.

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