Löwdin correlation energy density of the inhomogeneous electron liquid in some closed-shell molecules at equilibrium geometry
Faculty of Sciences. Chemistry
Physics and chemistry of liquids. - London
, p. 484-490
University of Antwerp
Using existing theoretical studies, we point out that the dominant variable in determining Lwdin correlation energies per electron Ec/N of isoelectronic series of molecules at equilibrium is the total number of electrons. This turns out to be Ec/N = -0.033 ± 0.003 a.u. for CH4, NH3, H2O and HF (N = 10), and Ec/N = -0.039 ± 0.007 for some 20 Si-containing molecules in the series SiXnYm. Following earlier work of March and Wind on atoms, some proposals are then made as to a possible explanation of such behaviour. A test is proposed, via low-order Mller-Plesset perturbation theory, as to whether the Lwdin correlation energy density åc(r) is, albeit approximately, a local functional åc(ñ) of the ground-state density for molecules at equilibrium. Such an LDA assumption would imply that åc(ñ) is quantitatively linear in ñ(r), for closed-shell molecules at equilibrium, at least for the light atomic components treated here. This, in turn implies that the dominant effect of the Lwdin correlation energy for closed-shell molecules at equilibrium is merely to shift the chemical potential.