Coulson–Fischer theory
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.
