In situ XAFS and XRD studies of pressure-induced local structural change in liquidAgI

Abstract

In order to examine the pressure-induced structural change of liquid silver iodide (AgI),high-pressure and high-temperature in situ x-ray absorption fine structure (XAFS) and x-raydiffraction (XRD) studies have been carried out up to 1200 K and 6 GPa. The modificationsin the x-ray absorption near edge structure (XANES) spectra and x-ray structure factors,S(Q), with increasing pressure provide evidence for changes in the short-range order of liquidAgI. The I–Ag bond length in liquid AgI increases by compression up to 2 GPa, whichproposes that components with higher coordination than fourfold are introduced. The I–Agbond length decreases monotonically with compression above 2 GPa, indicating that thestructural change involving a coordination-number change is completed below 2 GPaand then a high-pressure form of liquid AgI is stabilized. Comparing the I–Agbond lengths of liquid AgI with those of crystalline phases, we conclude that thehigh-pressure form of liquid AgI has a rocksalt-like structure with large vacancies.