Structural analysis of AgxCu1-xI (0.75 <= x < 1.00) in the superionic phase using solid Cu-63 NMR and X-ray diffraction methods

Two types of Cu-63 NMR signals and X-ray diffraction patterns of AgxCu1-xI (0.75 less than or equal to x < 1.00) were observed in the gamma-phase (zin cblende) to a-phase (body-centered cubic) transition. The high-field signal of Cu-63 NMR in the alpha-phase structure is considered to be due to the p ositive Cu ion mainly in the octahedral 6(b) position and partially in the tetrahedral 12(d) position, by comparison with the Cu chemical shielding ca lculations of three types of trigonal 24(h) CuI32-, tetrahedral 12(d) CuI43 -, and octahedral 6(b) CuI65- complexes using the ab initio GAUSSIAN94 prog ram with a double-zeta basis set. The Ag and Cu chemical shieldings of the metal complexes are explained mainly by the paramagnetic term. (C) 1999 Els evier Science B.V. All rights reserved.