Ab Initio Studies of Liquid and Amorphous Ge

TL;DR

This paper reviews ab initio molecular dynamics calculations of the dynamic structure factor S(k,omega) for liquid and amorphous germanium, demonstrating qualitative agreement with experimental data and validating the computational approach.

Contribution

The study applies ab initio molecular dynamics to compute S(k,omega) for liquid and amorphous Ge, showing it can produce results consistent with experiments.

Findings

Qualitative agreement of liquid Ge S(k,omega) with inelastic X-ray scattering data.

Qualitative agreement of amorphous Ge S(k,omega) with experimental results.

Ab initio approach is effective for modeling dynamic properties of disordered materials.

Abstract

We review our previous work on the dynamic structure factor S(k,omega) of liquid Ge (l-Ge) at temperature T = 1250 K, and of amorphous Ge (a-Ge) at T = 300 K, using ab initio molecular dynamics [Phys. Rev. B67, 104205 (2003)]. The electronic energy is computed using density-functional theory, primarily in the generalized gradient approximation, together with a plane wave representation of the wave functions and ultra-soft pseudopotentials. We use a 64-atom cell with periodic boundary conditions, and calculate averages over runs of up to 16 ps. The calculated liquid S(k,omega) agrees qualitatively with that obtained by Hosokawa et al, using inelastic X-ray scattering. In a-Ge, we find that the calculated S(k,omega) is in qualitative agreement with that obtained experimentally by Maley et al. Our results suggest that the ab initio approach is sufficient to allow approximate calculations of S(k,omega) in both liquid and amorphous materials.