Anharmonic correlated Debye model Debye-Waller factors

Anharmonic correlated Debye model has been derived for calculation and analysis of extended X-ray absorption fine structure (EXAFS) cumulants using an anharmonic effective potential that takes into account all nearest neighbor interactions of absorber and backscattering atoms. Dispersion relation has been considered, and anharmonic effects are included based on cumulant expansion. Analytical expressions for the first, second, third, and fourth EXAFS cumulants have been derived. They contain anharmonic effective potential parameters. Numerical calculations have been applied to Cu, where Morse potential is used to characterize the interaction between each pair of atoms. The results are found to be in good agreement with experiment.