Structural, vibrational, and dynamic properties of Ge-Ga-Te liquids with increasing connectivity: A combined neutron scattering and molecular dynamics study

Abstract

The physical properties of several compositions of ${\mathrm{Ge}}_{x}{\mathrm{Ga}}_{x}{\mathrm{Te}}_{100\ensuremath{-}2x}$ liquids ($x=6$, 10, 14%) are studied using a combination of density functional based molecular dynamics simulations and neutron experiments. We investigate structural properties including structure factors, pair distribution functions, angular distributions, coordination numbers, neighbor distributions and compare the results with diffraction experiments. We find that Ga is essentially in tetrahedral configuration and also affects the tetrahedral character of germanium when the results are compared to similar telluride liquids, while Te atoms display a coordination number that is larger than 2 and depend substantially on composition. The vibrational density of states is also measured from inelastic neutron scattering and compared to the simulated counterpart which exhibits a very good agreement at low frequency. We finally determine the dynamics of the melts by evaluating the diffusivity and relaxation properties. These reveal that Ge-Ga-Te melts are extremely fragile ($\mathcal{M}\ensuremath{\simeq}139$), similarly to Ge-Sb-Te liquids.