Modelling X-ray scattering factors from fluids of some fluorinated molecules and related compounds

摘要

There is current interest, both for basic science and technological applications, in fluorocarbons such as CF _4 and the related molecules. Here we first report a Hartree-Fock calculation of the ground-state electron density in the octahedral molecule SF _6 using the experimentally determined bond length. From this density, the number of electrons lying inside a sphere of radius r, denoted by Q(r), centred on the S nucleus has been extracted. The X-ray scattering factor f(k) is then modelled using Q(r) and compared with f(k) for the isoelectronic united atom ytterbium. The molecule CF _4, together with its isoelectronic partners PF _3, CrF _2 and AsF, is again compared with regard to f(k) with the united atom Mo. Finally, interest in modelling PbF is pointed out, in relation to the quantum-chemical theory already available.