Molecular Dynamics Simulation of Liquid Thallium

Abstract

The EAM potential for liquid thallium was proposed based on the experimental data for the pair correlation function, density, energy, and compressibility at 588 K. The properties of thallium models on the binodal were calculated to temperatures of 3000 K. Good agreement with experiment was obtained for density (to 1200 K), energy (to 3000 K), self-diffusion and viscosity coefficients (to 800 K), and with the existing pair correlation functions (to 973 K). The parameters of the EAM potential that are responsible for highly compressed states were calculated from the form of the shock adiabat of thallium: neglecting the electronic contributions to energy and pressure (EAM-1) and including these contributions using the free electron model (EAM-2). Two corresponding series of models were constructed under shock compression conditions to a pressure of 159 GPa. Inclusion of the electronic contributions lowers the temperature on the shock adiabat at Z = 1.8 by ∼23%. The cold pressure isotherms (at 298 K) calculated with both potentials are in good agreement with each other and with the isotherm of the real static compression of thallium to pressures of 137 GPa. For thallium nanoclusters with sizes from 13 to 5083 atoms, the excess surface energy was calculated, which is lower in the macroscopic limit by 15–20% than the surface tension of real thallium.