Structure and dynamics of a Ag-doped chalcogenide glass: an \textbf{\textit{ab initio}} study

The vibrational properties of a ternary glassy chalcogenide material, Ag$_{\mathrm{20}}$Ge$_{\mathrm{28}}$Se$_{\mathrm{52}}$, are analyzed. The vibrational density of states and atomic participation ratios calculations revealed that Se atoms are a major contributor across the vibrational spectrum. The abrupt change and plateau of the stretching character may be due to vibrational contribution changes and a difference in the rate of change for the Ge and Se atoms, respectively. The divergence of the perpendicular phase quotient is due to the rocking motion of a Ge-Ge compound. A1 breathing modes of the corner-sharing tetrahedra showed that these breathing modes are non-local and involve the mixing of modes of different symmetry resulting in two bands of A1 breathing modes.