  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.
