| Popis: |
The extended x-ray absorption fine structure (EXAFS) has been measured in the superionic phases of the Cu and Ag halides and chalcogenides. Cul and Cu 2 Se, both of which have an FCC anion lattice in the α phase, are discussed as representative examples. In both cases the excluded volume model provides an accurate description of the near neighbor cation-anion pair correlation function. It is found, however, that a significant fraction of the Cu ions occupy the octahedral sites in α-Cul but not for α-Cu 2 Se. For Cu 2 Se the Cu ions are predominately confined to the tetrahedral regions of the Se FCC lattice. The lack of octahedral occupation may result from larger Cu-Cu interactions for octahedral ions in the denser superionic material, Cu 2 Se. |
