Theoretical Debye-Waller factors of α-MoO3 estimated by an equation-of-motion method

Abstract

EXAFS oscillations of MoO3, which has a highly asymmetric local structure, have been calculated using backscattering amplitudes and phase shifts derived from the FEFF8 code and using Debye-Waller factors from an equation-of-motion method. They were compared with polarization-dependent empirical EXAFS data of the α-MoO3 single crystal at various temperatures. The theoretical EXAFS oscillations of Mo - O bonds for the [001] direction of the single crystal, where two symmetric Mo - O bonds exist, reproduced well the experimental data. On the other hand, the calculated data for the [100] direction, which contain two asymmetric Mo - O bonds with different bond lengths, agree well with the experimental data only after adjustment of the amplitude reduction factors for different Mo - O bonds. EXAFS oscillations of MoO3 powder were also calculated by the same method, and theoretical parameters that could reproduce the experimental data were found. These results suggest that the equation-of-motion method can evaluate the Debye-Waller factors efficiently in molecules with asymmetric local structures and can reduce curve-fitting parameters.