Calculation of electron momentum distributions using density functional theory

Abstract

The theoretical momentum profiles (TMPs) for all the valence orbitals of the hydrides CH4, NH3, H2O, HF, SiH4, PH3, H2S, and HCl are calculated using density functional theory (DFT) methods and compared with both configuration interaction (CI) calculations of the ion-neutral overlap and available experimental data. In all cases, it is found that DFT provides, within either the local or nonlocal approximation for the exchange and correlation potential, a close match to the experimental data and the CI calculations for shape. In cases where correlation and relaxation have been observed to have little effect on the shape of the TMP, DFT provides a close match in normalized intensity to the calculated momentum distribution as well. In cases where correlation and relaxation have a pronounced effect on the magnitude of the TMP, density functional theory is shown to consistently significantly overestimate the normalized intensity as predicted by the CI calculations. Use of a nonlocal functional is an improvement in this regard.