The structure of near stoichiometric Ge-Ga-Sb-S glasses: a reverse Monte Carlo study

TL;DR

This study uses neutron diffraction, X-ray diffraction, EXAFS, and reverse Monte Carlo simulations to elucidate the atomic structure of near-stoichiometric Ge-Ga-Sb-S glasses, revealing coordination numbers and local bonding environments.

Contribution

It provides detailed structural insights into Ge-Ga-Sb-S glasses using combined experimental and RMC modeling, highlighting the local bonding and coordination consistent with the chemically ordered network model.

Findings

Coordination numbers align with Mott-rule predictions.

Ga atoms have an average of 4 neighbors.

Sb exhibits longer S distances, indicating diverse local environments.

Abstract

The structure of Ge$_{22}$Ga$_3$Sb$_{10}$S$_{65}$ and Ge$_{15}$Ga$_{10}$Sb$_{10}$S$_{65}$ glasses was investigated by neutron diffraction (ND), X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) measurements at the Ge, Ga and Sb K-edges. Experimental data sets were fitted simultaneously in the framework of the reverse Monte Carlo (RMC) simulation technique. Short range order parameters were determined from the obtained large-scale configurations. It was found that the coordination numbers of Ge, Sb and S are around the values predicted by the Mott-rule (4, 3 and 2, respectively). The Ga atoms have on average 4 nearest neighbors. The structure of these stoichiometric glasses can be described by the chemically ordered network model: Ge-S, Ga-S and Sb-S bonds are the most important. Long Sb-S distances (0.3 - 0.4 {\AA} higher than the usual covalent bond lengths) are observed, suggesting that Sb atoms can be found in various local environments.