The Hubbard model for the hydrogen molecule

Using as an example the simplest case of a hydrogen molecule, the basis of the highly oversimplified Hubbard model is presented. This model attempts to understand the physics of both insulating and metallic systems in a unified picture, especially those metallic systems which include transition metals. The results of the analysis are compared with those obtained from independent electrons (delocalized model) which is used in the study of metals and from the Heitler–London (localized model) approach more appropriate for the treatment of molecules or insulating materials.