Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 131, Issue 5, Pages -Publisher
AIP Publishing
DOI: 10.1063/1.3187032
Keywords
carbon compounds; configuration interactions; density functional theory; isoelectronic series; molecular configurations; neptunium compounds; positive ions; protactinium compounds; SCF calculations; thorium compounds; uranium compounds; wave functions
Funding
- Danish Natural Science Research Council [272-06-0620]
- Norwegian Center for Theoretical and Computational Chemistry (CTCC)
- EC [JRP 01-12]
- SKB
- Swedish Research Council
- Carl Trygger Foundation
- Laboratoire de Physique des Lasers
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In a previous paper [Fromager , J. Chem. Phys. 126, 074111 (2007)], some of the authors proposed a recipe for choosing the optimal value of the mu 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 mu can be used for any molecule. Their calculations on neutral light element compounds all yielded mu(opt)=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 f(0) actinide compounds (ThO2, PaO2+, UO22+, UN2, CUO, and NpO23+). We find for these compounds that mu(opt)=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 (mu=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 (mu=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.
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