Dynamical Properties of the Liquid Polyvalent Elements: Soft Modes in Liquids

Abstract

Abstract We present investigations of the dynamical properties of liquid polyvalent metals and semimetals (with liquid Ge and As chosen as examples). The static liquid structure is calculated via molecular dynamics, based on exact interatomic forces from pseudopotential perturbation theory. The dynamical structure factor is calculated in a viscoelastic approximation. The static structure factor S(k) of the polyvalent elements is characterized by a side-peak or shoulder to the main peak at k = Qp. The side-peak is situated at k = 2kF where kF is the Fermi wavenumber. This shows that the structural anomaly is of electronic origin and may be interpreted in terms of a Peierls-like modulation of the packing of the atoms by the Friedel-oscillations in the interatomic forces. We demonstrate that the electronic effects also modify the dynamical structure factor and the dispersion relations of collective excitations and induce a modesoftening analogous to a Kohn-anomaly.