Local structures of AgBr
x
Cl1-x
solid solutions were investigated by means of Br K-edge EXAFS spectroscopy with the Br composition x varying from 0.05 to 1. The virtual crystal approximation did not hold as in other solid solutions investigated previously, although the Br-Ag bond distance noticeably varies with x. It was found for the first time that the x dependence of the Br-Ag distance is more significant at lower temperature than at room temperature. Such a new finding can be explained by the suppression of the long-range force with increasing temperature, compared with the short-range force.
Temperature-dependent Br K-edge EXAFS and XANES spectra of Br-adsorbed Pd ultrafine particles supported on SiO2 were measured and analyzed in order to characterize the surface chemical bondings between adsorbate Br and substrate Pd. It has been revealed that Br2 is not simply adsorbed on the surface but is dissociatively embedded into the Pd particles (embedded phase), resulting in the formation of PdBr2. On the other hand, BBr3 is dissociatively chemisorbed on the surface of the particles (chemisorbed phase). The Br-Pd interatomic distance in the chemisorbed phase is noticeably longer than that in the embedded one, and the Einstein frequency in the former is slightly smaller, indicating the softening of chemical bondings at the surface. XANES spectra have provided supplementary information on the difference between their electronic structures.
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