The temperature dependence of the Pt LIII- and I K-edge extended X-ray absorption fine-structure spectra of octahedrally coordinated Pt X62- complexes was experimentally investigated; not only for first-nearest neighbor shells, but also for higher-order shells. The second-order and third-order cumulants of a radial distribution function in the octahedral system were evaluated quantum-mechanically by using an interatomic potential which included third-order force constants. The experimentally obtained second-order cumulants agreed with the values that were expected on the basis of vibrational data, and the third-order cumulants successfully generated the anharmonic force constants. The contributions of bending motions to the cumulants of higher-order shells were considered in detail.

T.Yokoyama, Y.Yonamoto, T.Ohta, A.Ugawa: Physical Review B, 1996, 54[10], 6921-8