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Title: Multireference perturbation theory with improved virtualorbitals for radicals: More degeneracies, more problems
Authors: Ray, S. S
Manna, S
Ghosh, Anirban
Chaudhuri, R. K
Chattopadhyay, Sudip
Keywords: Improved virtual orbitals;Multireference perturbation theory;Radicals;Energy gaps;Statespecific method
Issue Date: 15-Feb-2019
Publisher: WILEY-VCH Verlag GmbH & Co.
Citation: International Journal of Quantum Chemistry, Vol.119, No. 4, e25776
Abstract: IVO‐SSMRPT is an affordable and accurate type of state‐specific multireference perturbation (SSMRPT) theory that adds dynamic correlation energy to improved virtual orbital (IVO) complete active space configuration interaction (CASCI) wave functions using a single‐root parametrization of multi‐root Hilbert‐space ansatz. We applied it to many chemically important di‐ and tri‐radicals to analyze the geometries and electronic properties of spectroscopic interest for both closed‐ and open‐shell singlet‐ and nonsinglet ground as well as excited states. We observed that IVO‐SSMRPT identifies optimized geometries, splitting between multiplets and frequencies for several radicals that are similar to those displayed by current generation state‐of‐the‐art methods but with admiringly decreased computational effort. This study illustrates the importance of having an accurate treatment of both nondynamical and dynamical correlation effects when examining multiradical species. Chemically and spectroscopically relevant answers can be obtained using our computationally tractable method. Our method will be a serviceable avenue for portraying open‐shell interactions in other radicals
Description: Restricted Access
ISSN: 1097-461X
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Appears in Collections:IIAP Publications

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