Non-locality in the exchange energy density of the inhomogeneous electron liquids in (HO)-O-2, NH3 and CH4 treated by Hartree-Fock theory

摘要

The exchange energy density has been studied by Hartree - Fock (HF) theory in the 10-electron molecules H2O, NH3 and CH4. The local density approximation (LDA) then provides a natural starting point for interpreting the HF data. Though LDA leads to 'shape similarity' for the exchange density of these three molecules, there is, ( a) no universality and (b) multivalued character at low densities. The low-density regime can, however, be interpreted in terms of a functional del rho/ln rho, with rho the ground-state electron density. This functional is here provided with a firm theoretical foundation. Thus, there is a 'cross-over' from LDA at high densities to a low-density functional in HF theory.