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TT: Fachverband Tiefe Temperaturen

TT 106: Frontiers of Electronic Structure Theory: Many-Body Effects, Methods (organized by O)

TT 106.1: Hauptvortrag

Donnerstag, 19. März 2015, 15:00–15:30, MA 004

Natural orbital functional theory with higher-order occupation probabilities — •Ralph Gebauer¹, Roberto Car², and Morrel Cohen^2,3 — ¹International Centre for Theoretical Physics (ICTP), Trieste, Italy — ²Department of Chemistry, Princeton University, Princeton, USA — ³Department of Physics and Astronomy, Rutgers University, USA

We introduce a novel energy functional for ground-state electronic-structure calculations. Its fundamental variables are the natural spin-orbitals of the implied singlet many-body wave function and their joint occupation probabilities. The functional derives from a sequence of controlled approximations to the two-particle density matrix. Algebraic scaling of computational cost with electron number is obtainable in general, and Hartree-Fock scaling in the seniority-zero version of the theory. Results obtained with the latter version for saturated small molecular systems are compared with those of highly-accurate quantum-chemical computations. The numerical results are variational, capturing most of the correlation energy from equilibrium to dissociation. Their accuracy is considerably greater than that obtainable with current density-functional theory approximations and with current functionals of the one-particle density matrix only.