CALCULATION AND USE OF FOURIER-TRANSFORMS OF COMPTON PROFILES

The expressions for the Fourier transforms of the Compton profiles have been derived, employing linear combinations of atomic orbitals based on Lowdin’s symmetrical orthogonalization method. The expressions as given are valid for crystals composed of atoms or ions with fully occupied subshells and, furthermore, complete occupation of the Brillouin zones is assumed. The derived formulae have been employed to show that the series-expansion method gives incorrect sigrs to some (or possibly all) inverse metric (or overlap) matrix elements of the fourth neighbours in the alkali halides. Because the effect of the third neighbours is negligible, only two orders of neighbours should be taken into account in such calculations. As a numerical application of the formulae the results for lithium hydride crystal have been presented. Comparison with available experimental data gives some indication that the Li ions may expand when placed in the LiH crystal, in contrast to all the quantum mechanical calculations performed so far, in which these ions are assumed to remain unchanged. © 1979 Taylor & Francis Ltd.