On the dependence of X-ray Debye–Waller parameters on atomic form factors

An analysis of powdered-diamond diffraction data with Hartree-Fock and standard molecular C atomic form factors yields the Debye-Waller parameters 0.20 ± 0.01 and 0.172 ± 0.009 Ų respectively. The lattice-dynamic value, which is calculated here from published phonon dispersion curves measured by inelastic neutron scattering, is 0.149-0.150 Ų at 298°K. It is shown that a small amount of an orbital product, χ^SCF_1s χ^STO_2s, in the core atomic scattering factor can dramatically alter the Debye-Waller parameter. For diamond, this latter scattering factor gives a value of 0.134 ± 0.009 Ų.