Diatomic generalized x-ray scattering factors: Results from Hartree–Fock electron density functions

Abstract

Generalized x-ray scattering factors based on multipole representation of the atoms have been calculated from Hartree–Fock Roothaan one-electron molecular density functions of first row diatomic hydrides (BH to FH) and the 14 electron series BF, N2, (1Σ)CO, and (3Π)CO. The effect of different truncation of the mutipole expansions is discussed for NH. Results for the other molecules from expansions up to quadrupolar terms on each center are discussed. The monopole scattering factors are virtually the same as Hartree–Fock atomic form factors except at low sinϑ/λ values. The dipole and quadrupole scattering factors are rather specific to the particular molecule for the valence region, but core polarization features are similar. Static charge properties of the molecule are accurately given by the generalized scattering factors. However, charge properties associated with the individual pseudoatoms are strongly dependent on truncation of the multipole expansion. The coherent x-ray scattering intensities of the molecule can be calculated from the generalized x-ray scattering factors with a maximum relative error no larger than 4×10−5.