The structure of vitreous and liquid GeSe 2: a neutron diffraction study

Abstract

High-quality neutron diffraction data are presented for GeSe 2 glass and liquid. In GeSe 2 glass at 10 K there is direct, clearly resolved evidence for edge-sharing of tetrahedra. C Ge(Ge) for dge-sharing tetrahedra measured in the glass (0.14), approaches that of the crystal (0.17). The Ge(Se 4) tetrahedron is the unit of short-range order in the glass, as it is in the crystal. The angle between neighboring corner-sharing tetrahedra in the glass is similar to that in the crystal. The tetrahedral building block persists in the liquid state at 1084 K, but it is broken up. The anomalous temperature dependence of the first sharp diffraction peak (FSDP) observed in the glass persists in the liquid. Experimentally, the height of the FSDP in the 1084 K liquid is 10% less than in the 10 K glass. The positions and the half-widths are identical. GeSe 2 retains considerable intermediate-range order in the liquid state. A comparison with molecular dynamics computer simulations is also presented.