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Ebisawa S, Tsutsumi T, Taketsugu T. Extension of Natural Reaction Orbital Approach to Multiconfigurational Wavefunctions. J Chem Phys 2022; 157:084118. [DOI: 10.1063/5.0098230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Recently, we proposed a new orbital analysis method, natural reaction orbital (NRO), which automatically extracts orbital pairs that characterize electron transfer in reaction processes by singular value decomposition (SVD) of the first-order orbital response matrix to the nuclear coordinate displacements (S. Ebisawa, M. Hasebe, T. Tsutsumi, T. Tsuneda, and T. Taketsugu, Phys. Chem. Chem. Phys. 24, 3532 (2022)). NRO analysis along the intrinsic reaction coordinate (IRC) for several typical chemical reactions demonstrated that electron transfer occurs mainly in the vicinity of transition states and in regions where the energy profile along the IRC shows shoulder features, allowing the reaction mechanism to be explained in terms of electron motion. However, its application has been limited to single configuration theories such as Hartree-Fock theory and density functional theory (DFT). In this work, the concept of NRO is extended to multiconfigurational wavefunctions and formulated as the multiconfiguration NRO (MC-NRO). The MC-NRO method is applicable to various types of electronic structure theories, including multiconfigurational theory and linear response theory, and is expected to be a practical tool for extracting the qualitative essence of a broad range of chemical reactions, including covalent bond dissociation and chemical reactions in electronically excited states. In this paper, we calculate the IRC for five basic chemical reaction processes at the level of the complete active space self-consistent field (CASSCF) theory and discuss the electron transfer by performing MC-NRO analysis along each IRC. Finally, issues and future prospects of the MC-NRO method are discussed.
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Kalpana P, Akilandeswari L. Can aromaticity trigger thermal [1,5]‐halogen shift towards the forbidden antarafacial mode?: A density functional case study. J PHYS ORG CHEM 2019. [DOI: 10.1002/poc.3991] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- P. Kalpana
- Department of ChemistrySri Sarada College for Women (Autonomous) Salem India
| | - L. Akilandeswari
- Department of ChemistrySri Sarada College for Women (Autonomous) Salem India
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Nohira H, Nohira T. Revisiting the von Neumann–Wigner noncrossing rule and validity of a dynamic correlation diagram method. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2019. [DOI: 10.1142/s0219633619500135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The noncrossing rule for potential energy surfaces can be applied only, as originally postulated by von Neumann and Wigner, to slowly occurring changes; it has, however, over many years, been widely used to rationalize fast chemical reactions. Taking the conversion of Dewar benzene to benzene as an example, we demonstrate a reaction that has a timescale for which crossings are allowed. Since it is now established that elementary chemical reactions proceed over ca. 10–100[Formula: see text]fs, as revealed experimentally by Zewail, the noncrossing rule cannot any longer be said to be valid for most chemical reactions. We further demonstrate that the mechanism of the chemiluminescent conversion of Dewar benzene to benzene is explained by an electronic state diagram derived using a dynamic correlation diagram method which allows crossings, whereas the reaction is not explained by a conventional approach, applying the noncrossing rule using a static correlation diagram method.
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Affiliation(s)
- Hiroyuki Nohira
- Department of Applied Chemistry, Faculty of Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338–8570, Japan
| | - Toshiyuki Nohira
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
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