Orbitals from local RDMFT: Are they Kohn-Sham or Natural Orbitals?

Abstract

Recently, an approximate theoretical framework was introduced, called local reduced density matrix functional theory (local-RDMFT), where functionals of the one-body reduced density matrix (1-RDM) are minimized under the additional condition that the optimal orbitals satisfy a single electron Schrödinger equation with a local potential. In the present work, we focus on the character of these optimal orbitals. In particular, we compare orbitals obtained by local-RDMFT with those obtained with the full minimization (without the extra condition) by contrasting them against the exact NOs and orbitals from a density functional calculation using the local density approximation (LDA). We find that the orbitals from local-RMDFT are very close to LDA orbitals, contrary to those of the full minimization that resemble the exact NOs. Since local RDMFT preserves the good quality of the description of strong static correlation, this finding opens the way to a mixed density/density matrix scheme, where Kohn-Sham orbitals obtain fractional occupations from a minimization of the occupation numbers using 1-RDM functionals. This will allow for a description of strong correlation at a cost only minimally higher than a density functional calculation.

References in corpus (5)

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Cited by in corpus (6)

• On derivatives of the energy with respect to total electron number and orbital occupation numbers. A critique of Janak's theorem
• RPA natural orbitals and their application to post-Hartree-Fock electronic structure methods
• Kinetic-Energy Density-Functional Theory on a Lattice
• Performance of the Constrained Minimization of the Total Energy in Density Functional Approximations: the Electron Repulsion Density and Potential
• Variational minimization scheme for the one-particle reduced density matrix functional theory in the ensemble N-representability domain
• Effective local potentials for density and density-matrix functional approximations with non-negative screening density