Theophilou, I., Lathiotakis, N. N., Marques, M. A. L., Helbig, N.

Generalized Pauli constraints in reduced density matrix functional theory
Journal of Chemical Physics **142**, (15),pp 154108/1-7 (2015)
Functionals of the one-body reduced density matrix (1-RDM) are routinely minimized under Coleman\'s
ensemble N-representability conditions. Recently, the topic of pure-state N-representability
conditions, also known as generalized Pauli constraints, received increased attention following the
discovery of a systematic way to derive them for any number of electrons and any finite dimensionality
of the Hilbert space. The target of this work is to assess the potential impact of the enforcement
of the pure-state conditions on the results of reduced density-matrix functional theory calculations.
In particular, we examine whether the standard minimization of typical 1-RDM functionals under the
ensemble N-representability conditions violates the pure-state conditions for prototype 3-electron
systems. We also enforce the pure-state conditions, in addition to the ensemble ones, for the same
systems and functionals and compare the correlation energies and optimal occupation numbers
with those obtained by the enforcement of the ensemble conditions alone.

TH-2015-21