A well-scaling natural orbital theory.
We introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree-Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals of the one-particle density matrix.
The Abdus Salam International Centre for Theoretical Physics, 34151 Trieste, Italy.
Ralph
R
Gebauer
Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854; mhcohen@prodigy.net rcar@princeton.edu.|Department of Chemistry, Princeton University, Princeton, NJ 08544.
Morrel H
MH
Cohen
Department of Chemistry, Princeton University, Princeton, NJ 08544; mhcohen@prodigy.net rcar@princeton.edu.|Department of Physics, Princeton University, Princeton, NJ 08544.
Roberto
R
Car
correlation; density matrix; electronic structure