Collect. Czech. Chem. Commun. 1988, 53, 2203-2213

Multiplicity of many-body wavefunctions using unrestricted Hartree-Fock reference functions

George D. Purvis, III, Hideo Sekino and Rodney J. Bartlett

Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, U.S.A.


Spin multiplicity formulae for the correlated Many Body Perturbation Theory (MBPT) and Coupled Cluster (CC) methods based upon an unrestricted Hartree Fock (UHF) reference function are presented and applied to evaluate the multiplicity in calculations of first row atoms. Spin projection in CC theory is discussed.