EXAFS cumulants and interatomic potentials

Temperature dependent EXAFS spectra of simple linear, octahedral and tetrahedral molecules have systematically been analyzed for the first and higher nearest neighbor (NN) shells including multiple-scattering contributions. The interatomic distances and the second-order cumulants obtained are in excellent agreement with the values given by the crystallographic and vibrational data, and the third-order cumulants have been estimated successfully. The stretching and bending anharmonic force constants have consequently been determined. The contribution of the stretching and bending force constants to the cumulants of higher NN shells was found to depend noticeably on molecular geometry. The dynamical effect of the scattering amplitude was also discussed.