Pressure Dependence of Anharmonic Effective Pair Potentials in Rock Salt Type AgI

Pressure dependence of anharmonic effective pair potentials V(u)=au2/2+bu3/3! for the I–Ag bond in rock salt type AgI has been investigated by EXAFS Debye‐Waller factors. EXAFS measurements near the I K‐edge were performed under pressure up to 6.0 GPa using a multi‐anvil high‐pressure device and synchrotron radiation from SPring‐8, Hyogo. The potential parameter a for rock‐salt type is 1.66(5) eV/A2 at 1.0 GPa and increases to 1.88(6) eV/A2 at 6.0 GPa. The phonon energies in rock salt type AgI under pressure have been estimated using the potential parameter a by calculating the dynamical matrix. The anharmonic effective pair potential for each phase is influenced by pressure and becomes steeper with increasing pressure while the extent of anharmonicity decreases with pressure.