Coulson-Fischer theory
Encyclopedia
In theoretical chemistry
and molecular physics
, Coulson-Fischer theory provides a quantum mechanical description of the electronic structure of molecules. The 1949 seminal work of Coulson
and Fischer established a theory of molecular electronic structure which combines the strengths of the two rival theories which emerged soon after the advent of quantum chemistry
- valence bond theory
and molecular orbital theory
, whilst avoiding many of their weaknesses. For example, unlike the widely used Hartree-Fock molecular orbital method, Coulson-Fischer theory provides a qualitatively correct description of molecular dissociative processes. The Coulson-Fischer wave function has been said to provide a third way in quantum chemistry. Modern valence bond theory
is often seen as an extension of the Coulson-Fischer method. For a single two-electron bond, the Coulson-Fischer theory is equivalent to the Generalized valence bond
method.
Theoretical chemistry
Theoretical chemistry seeks to provide theories that explain chemical observations. Often, it uses mathematical and computational methods that, at times, require advanced knowledge. Quantum chemistry, the application of quantum mechanics to the understanding of valency, is a major component of...
and molecular physics
Molecular physics
Molecular physics is the study of the physical properties of molecules, the chemical bonds between atoms as well as the molecular dynamics. Its most important experimental techniques are the various types of spectroscopy...
, Coulson-Fischer theory provides a quantum mechanical description of the electronic structure of molecules. The 1949 seminal work of Coulson
Charles Coulson
Charles Alfred Coulson FRS was an applied mathematician, theoretical chemist and religious author.His major scientific work was as a pioneer of the application of the quantum theory of valency to problems of molecular structure, dynamics and reactivity...
and Fischer established a theory of molecular electronic structure which combines the strengths of the two rival theories which emerged soon after the advent of quantum chemistry
Quantum chemistry
Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems...
- valence bond theory
Valence bond theory
In chemistry, valence bond theory is one of two basic theories, along with molecular orbital theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds...
and molecular orbital theory
Molecular orbital theory
In chemistry, molecular orbital theory is a method for determining molecular structure in which electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule...
, whilst avoiding many of their weaknesses. For example, unlike the widely used Hartree-Fock molecular orbital method, Coulson-Fischer theory provides a qualitatively correct description of molecular dissociative processes. The Coulson-Fischer wave function has been said to provide a third way in quantum chemistry. Modern valence bond theory
Modern valence bond theory
Modern valence bond theory is the term used to describe applications of valence bond theory with computer programs that are competitive in accuracy and economy with programs for the Hartree-Fock method and other molecular orbital based methods. The latter methods dominated quantum chemistry from...
is often seen as an extension of the Coulson-Fischer method. For a single two-electron bond, the Coulson-Fischer theory is equivalent to the Generalized valence bond
Generalized valence bond
The generalized valence bond method is one of the simplest and oldest valence bond method that uses flexible orbitals in the general way used by modern valence bond theory. The method was developed by the group of William A...
method.