Ab Initio Simulations For Expanded Gold Fluid In Metal-Nonmetal Transition Regime

Ab initio simulations based on quantum molecular dynamics have been performed to study the electrical and optical properties of expanded gold fluids from one to a sixth of the normal solid density and with temperatures varying from 5000 to 20 000 K. With decreasing density, the dynamic conductivity evolves from the characteristic of a metal to that of a nonmetal. The DC conductivity is given by fitting the dynamic conductivity using the Drude or Drude-Smith model. According to the shift of the central peak of dynamic conductivity, the change of the slope of DC conductivity with respect to temperature, and the appearance of the disconnected network in the charge density distribution, the metal-nonmetal transition of expanded gold fluids occurs in the vicinity of one-third of the normal solid density. In addition, as the density decreases, the localization of 6s and 5d states is observed in the density of states.