Molecular Application of a State Specific Multi-Reference Brillouin–Wigner Perturbation Theory*Supported by the Scientific and Technological Research Council of Turkey (TUBİTAK) under Grant No 2219-1/2013. (February 2016)

• Record Type: Journal Article
• Authors: Aksu, H.
• Is Part Of: Chinese physics letters. Volume 33:Number 2(2016:Feb.)
• Publication Date: 2016-02
• Subjects: 31.15.xp -- 31.50.−x -- 31.50.Bc; Physics -- Periodicals; Electronic journals; 530.05
• DOI: 10.1088/0256-307X/33/2/023102
• Languages: English
• ISSNs: 0256-307X

Abstract

Abstract : The single reference second order Brillouin–Wigner perturbation theory recently developed, which eliminates its size-extensivity error, has been generalized to state-specific, multi-reference (SS-MR), BWPT2 providing a size-extensive correction to the electron correlation problem for systems that demand the use of a multi-reference function. Illustrative numerical tests of the size-extensivity corrections are made for widely used molecules in their ground states, which are pronounced multi-reference characteristics. We have implemented two-reference and three-reference cases for CH2, BH and bond breaking process in the ground states of HF molecules. The results are compared with the rigorously size-extensive methods such as the Møller–Plesset perturbation theory, i.e., MP2, full configuration interaction (Full-CI) and allied methods using the same basis sets.