ASYMMETRY IN THE LOCAL STRUCTURAL ORDER IN ARSENIC CHALCOGENIDE GLASSES - HIGH-FIELD NMR IN CRYSTALLINE AND GLASSY AS2SE3

Nuclear magnetic resonance (NMR) of As-75 in crystalline and glassy sa mples of As2Se3 has been studied at magnetic fields up to 22 T. The re sults, which yield asymmetries in the electric field gradient at the a rsenic sites that disagree with those inferred from previous low field studies, are inconsistent with the predictions of a common model (Raf t Model) for the structure of glassy As2Se3 and other chalcogenide gla sses. This technique should be useful for many other solids that conta in one of the twenty elements whose nuclei have spin 3/2 and relativel y large quadrupole moment. (C) 1997 Published by Elsevier Science Ltd.