Multiple-Edge EXAFS Study of Solid and Liquid CuBr

Abstract
X-ray absorption measurements of solid and liquid CuBr have been carried out around the Cu and Br K-edge at 295, 400, 600, 670, 793 K. EXAFS data of both edges have been analyzed simultaneously, for the first time on a binary compound, by using the ab-initio multiple-scattering GNXAS method. Multiple-edge EXAFS refinement allowed us to obtain an accurate determination of the first-neighbor distribution as a function of temperature. Mean bond distance, variance and skewness of the distribution have been measured and their statistical errors evaluated. A slight contraction of the most probable Cu-Br bond-length is observed at high temperatures approaching the superionic and the liquid phases (T≥670K). The asymmetry of the first-neighbor distribution is found to increase at high-temperature. Evidence for nearly-covalent bonding is found in liquid CuBr.