Comment on "Generalization of the Kohn-Sham system that can represent arbitrary one-electron density matrices"

TL;DR

This paper critically examines van Dam's claims that a single-determinant wavefunction can represent any one-electron density matrix and that Koopmans theorem applies in 1RDM functional theory, providing counterarguments.

Contribution

The authors refute van Dam's claims by demonstrating that his assertions about representing arbitrary 1RDMs and applying Koopmans theorem are incorrect.

Findings

van Dam's claim about representing arbitrary 1RDMs is unfounded

van Dam's application of Koopmans theorem in 1RDMFT is invalid

The paper clarifies limitations of 1RDM functional theory

Abstract

Hubertus J. J. van Dam [Phys. Rev. A 93, 052512, 2016] claims that the one-particle reduced density matrix (1RDM) of an interacting system can be represented by means of a single-determinant wavefunction of fictitious non-interacting particles. van Dam introduced orbitals within a mean-field framework that produce energy levels similar to Hartree-Fock (HF) orbital energies, therefore he also claims that conventional analyses based on Koopmans theorem are possible in 1RDM functional theory (1RDMFT). In this comment, we demonstrate that both claims are unfounded.