<b><scp>Valence</scp></b>: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

Fletcher, Graham D.; Bertoni, Colleen; Keçeli, Murat; D‘Mello, Michael

doi:10.1002/jcc.25818

Cited by 3 publications

(1 citation statement)

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“…Although the VSVB method shares the same underlying concepts as the SCGVB method, the VSVB wave function with its additional constraints is not the same as the SCGVB wave functions. One advantage of VSVB theory, as implemented in the VALENCE software package, 72 is that the calculations are well suited for today's large heterogeneous, multiprocessor computers.…”

Section: Overview Of Scgvb Theorymentioning

confidence: 99%

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Dunning

Cooper

et al. 2021

J. Phys. Chem. A

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Spin-Coupled Generalized Valence Bond (SCGVB) theory provides the foundation for a comprehensive theory of the electronic structure of molecules. SCGVB theory offers a compelling orbital description of the electronic structure of molecules as well as an efficient and effective zero-order wave function for calculations striving for quantitative predictions of molecular structures, energetics and other properties. The orbitals in the SCGVB wave function are usually semi-localized and, for most molecules, can be interpreted using concepts familiar to all chemists (hybrid orbitals, localized bond pair, lone pairs, etc.). SCGVB theory also provides new perspectives on the nature of the bonds in molecules such as C2, Be2 and SF4/SF6. SCGVB theory contributes unparalleled insights into the underlying cause of the first-row anomaly in inorganic chemistry as well as the electronic structure of organic molecules and the electronic mechanisms of organic reactions. The SCGVB wave function accounts for nondynamical correlation effects and, thus, corrects the most serious deficiency in molecular orbital (RHF) wave functions. Dynamical correlation effects, which are critical for quantitative predictions, can be taken into account using the SCGVB wave function as the zero-order wave function for multireference configuration interaction or coupled cluster calculations.* In prior articles in the literature the Spin-Coupled Generalized Valence Bond wave function has usually been referred to as the Spin-Coupled Valence Bond (SCVB) wave function or the full Generalized Valence Bond (full GVB) wave function. These wave functions are identical; to prevent confusion, the authors have adopted the allencompassing SCGVB name. Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds3 and recoupled pair bond dyad. 36 The SCGVB wave function describes molecules in terms of orbitals that are optimized at each geometry, allowing the atomic orbitals to change as a result of molecule formation. In addition to the changes in the orbitals, optimization of the general spin function used in the SCGVB wave function allows the spin function to change from that appropriate for the separated atoms or fragments to that appropriate for the molecule. SCGVB theory addresses a major limitation of RHF theory, providing an excellent zero-order description of molecules that require multiconfiguration descriptions, the making/breaking of bonds, and many chemical reactions and excited states. For most molecules, the SCGVB wave function captures the essential features of the FORS/CASSCF wave functions, with much reduced complexity compared to these latter wave functions.

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Section: Overview Of Scgvb Theorymentioning

confidence: 99%

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Dunning

Cooper

et al. 2021

J. Phys. Chem. A

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Spin-Coupled Generalized Valence Bond Theory: An Appealing Orbital Theory of the Electronic Structure of Atoms and Molecules

Dunning

Karadakov

2024

Comprehensive Computational Chemistry

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Prediction of correlation energies using variational subspace valence bond

Fletcher

Bertoni

Keçeli

et al. 2022

The Journal of Chemical Physics

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In the variational subspace valence bond (VSVB)1 method the electronic orbitals comprising the wave function correspond to chemically meaningful objects such as bonds, lone pairs, atomic cores, and so on. Selected regions of a molecule (for example, a single chemical bond, as opposed to all the bonds) can be modeled with different levels of basis set and possible methods for modeling correlation from the other regions. The interactions between the components of a molecule (say, a bond and a neighboring orbital) can then be studied in detail for their impact on a chemical phenomenon while avoiding the expense of necessarily applying the higher levels and methods to the entire molecule. This work presents the theoretical basis for modeling correlation effects between specific electron pairs by incorporating terms in the inter-electronic coordinates (') into VSVB. The approach is validated with calculations on small systems using single-reference wave functions.

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Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

Cited by 3 publications

References 46 publications

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Spin-Coupled Generalized Valence Bond Theory: An Appealing Orbital Theory of the Electronic Structure of Atoms and Molecules

Prediction of correlation energies using variational subspace valence bond

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