NMR study on the chemical bonding and the ionic conductivity in noble metal halides

The temperature dependence of nuclear relaxation rate, 1/T-1 has been measu red for copper halides, CuX with X being Cl, Br and I. The results axe inte rpreted in terms of the quadrupole relaxation due to lattice vibrations and defect motions. The data of 1/T-1 axe compared with a model calculation ba sed on an ionic model. in which the degree of covalent bonding lambda (0) i s estimated to be 63% for CuCl, 49% for CuBr and 27% for CuI. The Ao values for copper halides axe compared with previous values for silver and sodium halides, and also compared with the ionicity of A(N)B(8-N) binary compound s. The relation between lambda (0) values and migration energies Em for cat ion vacancies derived from 1/T-1 data is discussed in connection with the s uperionicity of alpha -AgI.