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Density-functional theory; N-representability problem; electron pair density

Using the constrained search and Legendre-transform formalisms, one can derive “generalized” density-functional theories, in which the fundamental variable is either the electron pair density or the second-order reduced density matrix. In both approaches, theN-representability problem is solved by the functional, and the variational principle is with respect to all pair densities (density matrices) that are nonnegative and appropriately normalized. The Legendre-transform formulation provides a lower bound on the constrained-search functional. Noting that experience in density-functional and density-matrix theories suggests that it is easier to approximate functionals than it is to approximate the set ofN-representable densities sheds some light on the significance of this work.

Paul W Ayers¹ Mel Levy^{2 3}

1. Department of Chemistry, McMaster University, Hamilton, Ontario - L8S 4M1, Canada
2. Department of Physics, North Carolina A&T University, Greensboro, NC - 27411, USA
3. Department of Chemistry, Tulane University, New Orleans, LA - 70118, USA

Published

September 2005