STRUCTURE-ANALYSIS OF METAL(I) HALIDE MIXED-CRYSTAL BY CU-63 MASNMR AND X-RAY-DIFFRACTION METHODS .3. CUCLXBR1-X CRYSTAL

Mixed CuClxBr1-x crystals were prepared by the melt-annealing method and by a conversion process. X-Ray diffraction curves indicated that the former method produced a completely solid solution and the latter produced a nearly solid solution. Cu-63 MAS NMR spectra of the sample made by the former method were broad, while those made by the latter process were sharp and spread over a range of shifts between solid CuCl and CuBr. The spectra were attributed to the overlapping peaks of five structural species: CuCl4, CuCl3Br, CuCl2Br2, CuClBr3 and CuBr4. The CuCliBr4-i (i = 0-4) species are believed to be composed of lattice sites of C1, C2v, C3v or T(d) symmetries. The NMR spectra were separated into several Gaussian peaks by a curve fitting calculation with a nonlinear optimization method. The lineshape parameters (chemical shift and half width) obtained for the solid solutions can be explained by considering components which involve second-order quadrupolar coupling tensors. Various values of quadrupolar coupling tensors are explainable by different tetrahedral symmetries of CuCliBr4-i species in the crystal.