Ab initio molecular-dynamics study of the structural and transport propertiesof liquid germanium

We describe the results of ab initio molecular-dynamics simulations of liquid Ge at five temperatures ranging from 1250 to 2000 K. The electronic structure is calculated using the local-density approximation and generalized norm-conserving pseudopotentials. The calculations yield the pair correlation function, the static structure factor, the bond-angle distribution function, the electronic density of states, the atomic self-diffusion coefficient, and finally the ac conductivity. Near melting, the structure factor has the experimentally observed shoulder on the high-k side of the principal peak, which becomes progressively less distinct at higher temperatures. The bond-angle distribution function indicates the persistence of covalent bonding for shorter bond lengths in the liquid state. The electronic density of states is metallic at all the temperatures with a pseudogap at a binding energy of 4.6 eV. The diffusion constant shows a sharp rise between 1250 and 1500 K (1.2×{}10^-4--2.0×{}10^-4 cm² s^-1 ) and increases less rapidly at higher temperatures, to only 2.3×{}10^-4 cm² s^-1 at 2000 K.