Results 231 to 240 of about 49,790 (296)

Automatic Selection of Active Orbitals from Generalized Valence Bond Orbitals

The Journal of Physical Chemistry A, 2020
The accurate multireference (MR) calculation of a strongly correlated chemical system usually relies on a correct preselection of a small number of active orbitals from numerous molecular orbitals. Currently, the active orbitals are generally determined by using a trial-and-error method. Such a preselection by chemical intuition and personal experience
Jingxiang Zou, Ke Niu, Haibo Ma, Shuhua Li, Weihai Fang   +4 more
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Generalized valence bond description of simple ylides

Journal of the American Chemical Society, 1983
The electronic structures of the simplest ylides of nitrogen, oxygen, phosphorus, and sulfur have been determined from ab initio molecular orbital theory at the generalized valence bond (GVB) + POL-CI level. The calculations were performed with double-zeta quality basis sets augmented by polarization (d) functions on the heavy atoms and a set of ...
David A. Dixon, Thom H. Dunning, Robert A. Eades, Paul G. Gassman   +3 more
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ChemInform Abstract: THE GENERALIZED VALENCE BOND DESCRIPTION OF ALLYL RADICAL

Chemischer Informationsdienst, 1975
GEORGE LEVIN, W. A. III GODDARD
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Computational developments in generalized valence bond calculations

Journal of Computational Chemistry, 1996
In this article a procedure for generating starting orbitals for generalized valence bond (GVB) calculations is presented. This is achieved by selecting orbitals which correspond to specific bonds or electron pairs. These orbitals can be identified from the localized molecular orbitals, for both occupied and virtual orbitals, which are obtained through
Youliang Wang, Raymond A. Poirier
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Generalized valence bond molecular dynamics at constant temperature

Molecular Physics, 1996
The Nose–Hoover chain thermostat of Martyna, Klein and Tuckerman has been adapted to work with our generalized valence bond ab initio molecular dynamics (AIMD) method, allowing us to perform AIMD in the canonical ensemble (constant number of particles temperature and volume).
DOUGLAS GIBSON, EMILY CARTER
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ChemInform Abstract: Valence Bonds in the Main Group Elements. Generalized Valence Bond Description

ChemInform, 1991
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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Excitation energies from time-dependent generalized valence bond method

Theoretical Chemistry Accounts, 2015
A generalized valence bond perfect-pairing (GVBPP) wavefunction has been extensively used in computational chemistry methods due to its multiconfigurational character, which captures in an inexpensive way static electron correlation. GVB-PP has been mostly applied to ground states and not much is known about its performance in predicting electronic ...
Koushik Chatterjee, Katarzyna Pernal
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Connections between coupled cluster and generalized valence bond theories

The Journal of Chemical Physics, 2001
We explore the fundamental connections between certain approximate coupled cluster (CC) and generalized valence bond (GVB) wave functions. We show that the GVB restricted configuration interaction (GVB-RCI) wave function can be associated with a compact CC expansion in the valence space.
Troy Van Voorhis, Martin Head-Gordon
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Implementation of generalized valence bond-inspired coupled cluster theories

The Journal of Chemical Physics, 2002
We present an implementation of the recently proposed imperfect pairing (IP) and generalized valence bond restricted coupled cluster (GVB-RCC) methods. Our algorithm centers on repeated construction of Coulomb and exchange matrices. These operations are the computational bottleneck, scaling with the third power of system size for large systems.
Troy Van Voorhis, Martin Head-Gordon
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Calculations using generalized valence bond based Møller–Plesset perturbation theory

The Journal of Chemical Physics, 2001
This work presents calculations on small molecules using second-order Møller–Plesset perturbation theory with a generalized valence bond reference wave function. Møller–Plesset perturbation theory applied to a generalized valence bond reference (GVB-MP2) currently provides the best tradeoff between accuracy and computational feasibility among the ...
Mihir Sejpal, Richard P. Messmer
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