J. Phys. IV France 7 (1997) C2-155-C2-156
Ab Initio XAFS Debye-Waller FactorsA.V. Poiarkova1 and J.J. Rehr2
1 Physics Department, Box 351560, University of Washington, Seattle, WA 98195-1560 U.S.A.
2 Physics Department, Box 351560, University of Washington, Seattle, WA 98195-1560, U.S.A.
An efficient, finite temperature, equation of motion method is introduced for calculations of the meansquare relative displacements σ2 in XAFS Debye-Waller factors. Instead of calculating projected densities of modes, the calculations are based on the displacement-displacement correlation function and done in real time, over a few vibration cycles. Results for the Debye-Waller factors are found to be accurate to within about 15% percent at all temperatures. We also discuss how force constants used in the calculations can be obtained from ab initio Car-Parrinello/molecular dynamics calculations. Tests of the method are presented based on the Wiggs-Jónsson plane-wave pseudopotential code [Comp. Phys. Comm. 87, 319 (1995)]. Application to XAFS Debye-Waller factors in biological molecules is discussed.
© EDP Sciences 1997