THE COORDINATION ENVIRONMENT OF AG AND CU IN TERNARY CHALCOGENIDE GLASSES

An analysis is made of the information provided by the method of isoto pic substitution in neutron diffraction on the metal atom coordination environment in M-A-X glasses, where M denotes Ag or Cu, A a Group IVB or VB element, and X a chalcogen. It is found that the M-X coordinati on number is low (similar to 3-4) but there is no clear correlation be tween its precise value and whether the material is a semiconductor or fast-ion conductor. When the concentration of M is high it is possibl e to measure the M-M partial pair distribution function g(M-M)(r) In t hose systems for which results are available it is found that, irrespe ctive of the electrical conductivity mechanism, short M-M nearest-neig hbour distances are present. However, the first peak in g(M-M)(r) is m ore clearly defined in the case of semiconducting glasses.