Nonstandard N-representability constraints and their application to chemical and physical systems
Dimitri Van Neck, Brecht Verstichel, Helen van Aggelen, Patrick Bultinck, Paul W. Ayers · Ghent University Academic Bibliography (Ghent University) · 2011
The accuracy of variationally determined two-body density matrices depends crucially on the N-representability conditions that are imposed. We will discuss some nonstandard types of constraints that can be added to the 2-index constraints to obtain accuracies that are, in some cases, comparable to that obtained by including the computationally much more expensive 3-index conditions. The constraints are illustrated by applications to molecules and to the Hubbard hamiltonian in one and two dimensions.