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Improved virtual orbitals in state specific multireference perturbation theory for prototypes of quasidegenerate electronic structure

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dc.contributor.author Sinha Ray, S
dc.contributor.author Ghosh, P
dc.contributor.author Chaudhuri, R. K
dc.contributor.author Chattopadhyay, S
dc.date.accessioned 2020-11-27T12:51:20Z
dc.date.available 2020-11-27T12:51:20Z
dc.date.issued 2017-02
dc.identifier.citation Journal of Chemical Physics, Vol. 146, No. 6 , 064111 en_US
dc.identifier.issn 1089-7690
dc.identifier.uri http://prints.iiap.res.in/handle/2248/7492
dc.description Restricted Access © American Chemical Society http://dx.doi.org/10.1063/1.4975322 en_US
dc.description.abstract The state-specific multireference perturbation theory (SSMRPT) with an improved virtual orbital complete active space configuration interaction (IVO-CASCI) reference function [called as IVO-SSMRPT] is used to investigate the energy surface, geometrical parameters, molecular properties of spectroscopic interest for the systems/situations [such as BeH2, BeCH2, MgCH2, Si2H4, unimolecular dissociation of H2CO, and intramolecular reaction pathways of 1,3-butadiene] where the effect of quasidegeneracy cannot be neglected. The merit of using the IVO-CASCI rather than complete active space self-consistent field (CASSCF) is that it is free from iterations beyond those in the initial SCF calculation and the convergence difficulties that plague CASSCF calculations with increasing size of the CAS. While IVO-CASCI describes the non-dynamical correlation, the SSMRPT scheme is a good second-order perturbative approximation to account for the rest of the correlation energy. Our IVO-SSMRPT method is instrumental in avoiding intruder states in an size-extensive manner and allows the revision of the content of wave function in the model space. It can treat model as well as real systems with predictive accuracy, as is evident from the fairly nice accordance between our estimates, and high-level theoretical results. Our estimates also corroborate well with some experimental findings. en_US
dc.language.iso en en_US
dc.publisher American Institute of Physics en_US
dc.subject Basis sets en_US
dc.subject Transition state theory en_US
dc.subject Excited states en_US
dc.subject Wave functions en_US
dc.subject Chemical bonds en_US
dc.title Improved virtual orbitals in state specific multireference perturbation theory for prototypes of quasidegenerate electronic structure en_US
dc.type Article en_US


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