The generalized valence bond (GVB) is a method in
valence bond theory
In chemistry, valence bond (VB) theory is one of the two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on how the atomic orbitals of ...
that uses flexible orbitals in the general way used by
modern valence bond theory. The method was developed by the group of
William A. Goddard, III around 1970.
Theory
The generalized
Coulson–Fischer theory for the
hydrogen molecule, discussed in
Modern valence bond theory, is used to describe every electron pair in a molecule. The orbitals for each electron pair are expanded in terms of the full basis set and are non-orthogonal. Orbitals from different pairs are forced to be
orthogonal
In mathematics, orthogonality is the generalization of the geometric notion of '' perpendicularity''.
By extension, orthogonality is also used to refer to the separation of specific features of a system. The term also has specialized meanings in ...
- the strong orthogonality condition. This condition simplifies the calculation but can lead to some difficulties.
Calculations
GVB code in some programs, particularly
GAMESS (US)
General Atomic and Molecular Electronic Structure System (GAMESS (US)) is computer software for computational chemistry program. The original code started on October 1, 1977 as a National Resources for Computations in Chemistry project. In 1981, t ...
, can also be used to do a variety of restricted open-shell
Hartree–Fock calculations,
such as those with one or three electrons in two pi-electron molecular orbitals while retaining the degeneracy of the orbitals. This wave function is essentially a two-determinant function, rather than the one-determinant function of the restricted Hartree–Fock method.
References
Chemical bonding
Electronic structure methods
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