On the universality of the long-/short-range separation in multiconﬁgurational density-functional theory. II. Investigating f0 actinide species
2009 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, 054107Article in journal (Refereed) Published
In a previous paper [ Fromager et al., J. Chem. Phys. 126, 074111 (2007) ], some of the authors proposed a recipe for choosing the optimal value of the μ parameter that controls the long-range/short-range separation of the two-electron interaction in hybrid multiconfigurational self-consistent field short-range density-functional theory (MC-srDFT) methods. For general modeling with MC-srDFT methods, it is clearly desirable that the same universal value of μ can be used for any molecule. Their calculations on neutral light element compounds all yielded μopt = 0.4 a.u. In this work the authors investigate the universality of this value by considering “extreme” study cases, namely, neutral and charged isoelectronic f0 actinide compounds (ThO2, PaO2+, UO22+, UN2, CUO, and NpO23+). We find for these compounds that μopt = 0.3 a.u. but show that 0.4 a.u. is still acceptable. This is a promising result in the investigation of a universal range separation. The accuracy of the currently best MC-srDFT (μ = 0.3 a.u.) approach has also been tested for equilibrium geometries. Though it performs as well as wave function theory and DFT for static-correlation-free systems, it fails in describing the neptunyl (VII) ion NpO23+ where static correlation is significant; bending is preferred at the MC-srDFT (μ = 0.3 a.u.) level, whereas the molecule is known to be linear. This clearly shows the need for better short-range functionals, especially for the description of the short-range exchange. It also suggests that the bending tendencies observed in DFT for NpO23+ cannot be fully explained by the bad description of static correlation effects by standard functionals. A better description of the exchange seems to be essential too.
Place, publisher, year, edition, pages
2009. Vol. 131, 054107
IdentifiersURN: urn:nbn:se:su:diva-54866DOI: 10.1063/1.3187032OAI: oai:DiVA.org:su-54866DiVA: diva2:398755