Einstein and Debye models for EXAFS parallel and perpendicular mean-square relative displacements.
The correlated Einstein and Debye models for EXAFS parallel mean-square relative displacement (MSRD) are derived from the general expression in terms of eigenfrequencies and eigenvectors of the dynamical matrix, without ad hoc assumptions. The two models are generalized to parameterize also the EXAFS perpendicular MSRD. The physical meaning of Einstein frequencies, as well as the application of the Debye model to crystals with more than one atom per cell, are critically discussed.
Vaccari
M
M
Istituto Nazionale per la Fisica della Materia and Dipartimento di Fisica, Università di Trento, I-38050 Povo (Trento), Italy. vaccarj@science.unitn.it
Fornasini
P
P
D000465:Algorithms; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D011789:Quantum Theory; D014961:X-Ray Diffraction / Q000379:methods*