A Natural Orbital Diagnostic for Multiconfigurational Character in Correlated Wave Functions

@inproceedings{Gordon1999ANO,
  title={A Natural Orbital Diagnostic for Multiconfigurational Character in Correlated Wave Functions},
  author={Mark S. Gordon and Michael W. Schmidt and Galina M. Chaban and Kurt R. Glaesemann and Walter J. Stevens and Carlos Enrique Gonzalez},
  year={1999}
}
The natural orbitals and their corresponding occupation numbers are constructed for several interesting problems to demonstrate that the existence of negative natural orbital occupation numbers for single reference correlation methods provides a simple diagnostic for the need for a multiconfigurational description of the wave function.