Physics – Condensed Matter – Materials Science
Scientific paper
2007-02-16
Physics
Condensed Matter
Materials Science
11 pages, 8 figures
Scientific paper
10.1103/PhysRevB.76.014301
An approach is presented for theoretical calculations of the Debye-Waller factors in x-ray absorption spectra. These factors are represented in terms of the cumulant expansion up to third order. They account respectively for the net thermal expansion $\sigma^{(1)}(T)$, the mean-square relative displacements $\sigma^2(T)$, and the asymmetry of the pair distribution function $\sigma^{(3)}(T)$. Similarly, we obtain Debye-Waller factors for x-ray and neutron scattering in terms of the mean-square vibrational amplitudes $u^2(T)$. Our method is based on density functional theory calculations of the dynamical matrix, together with an efficient Lanczos algorithm for projected phonon spectra within the quasi-harmonic approximation. Due to anharmonicity in the interatomic forces, the results are highly sensitive to variations in the equilibrium lattice constants, and hence to the choice of exchange-correlation potential. In order to treat this sensitivity, we introduce two prescriptions: one based on the local density approximation, and a second based on a modified generalized gradient approximation. Illustrative results for the leading cumulants are presented for several materials and compared with experiment and with correlated Einstein and Debye models. We also obtain Born-von Karman parameters and corrections due to perpendicular vibrations.
Krappe H. J.
Rehr John J.
Rossner H. H.
Vila Fernando D.
No associations
LandOfFree
Theoretical X-Ray Absorption Debye-Waller Factors does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Theoretical X-Ray Absorption Debye-Waller Factors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Theoretical X-Ray Absorption Debye-Waller Factors will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-196274