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

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.