LOCAL-STRUCTURE AND DYNAMICS IN AGI STUDIED BY EXAFS AND MOLECULAR-DYNAMICS

EXAFS of AgI from 20 to 450 K has been analyzed by the cumulant method. The distribution of Ag-I distances agrees with the excluded-volume model of Boyce and Hayes. It is however suggested that in beta phase the distribution can be accounted for by an anharmonic effective pair potential with temperature-independent shape. EXAFS reveals a high degree of correlation of vibrational motion of silver and iodine, both in beta and a phases. I-Ag and I-I distributions obtained from EXAFS in beta phase are compared with molecular dynamics (MD) calculations; the observed discrepancies suggest that EXAFS could be utilized to check the MD interatomic potentials.