Structure of rare-earth chalcogenide glasses by neutron and x-ray diffraction

The method of neutron diffraction with isomorphic substitution was used to measure the structure of the rare-earth chalcogenide glasses [Formula: see text](Ga₂ X ₃)_0.33(GeX ₂)_0.60 with [Formula: see text] or Ce and [Formula: see text] or Se. X-ray diffraction was also used to measure the structure of the sulphide glass. The results are consistent with networks that are built from GeX ₄ and GaX ₄ tetrahedra, and give R-S and R-Se coordination numbers of 8.0(2) and 8.5(4), respectively. The minimum nearest-neighbour R-R distance associated with rare-earth clustering is discussed.