Compton Profile of LiH

A Compton-profile measurement of polycrystalline LiH has been made using 59.54-keV $\gamma$ rays of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$. Fairly good agreement is found with a previous Compton-profile measurement at 17 keV using $\mathrm{Mo}K\alpha$ x rays. A simple two-parameter theory is used in which a radial phase dependence is introduced for each of the two ${\mathrm{H}}^{-}$ electrons. Good agreement is obtained with the measured Compton profile and previously measured scattering factors. This is in contrast with previous theories which, though obtaining good agreement with the measured scattering factors, consistently predicted narrower Compton profiles than were experimentally measured. A tight-binding calculation of the Compton profile of LiH was also made using Kunz local-orbital wave functions, which in contrast to previously used simple screened-hydrogenic wave functions have the important feature that first-order overlap has been taken into account. The previously neglected ${\mathrm{Li}}^{+}$-${\mathrm{Li}}^{+}$ overlaps are shown to be non-negligible and are included. This ab initio calculation, similar to previous theories, predicts a narrower Compton profile than experimentally measured.