  The Ragot-Cortona model of local correlation energy (J. Chem. Phys. 121, 7671
(2004)) revisits the initial approach of Colle and Salvetti [Theo. Chim. Acta
37, 329 (1975)] in order to reinstate the kinetic contribution Tc to the total
correlation energy Ec. In this work, the one-electron reduced density-matrix
underlying the amended model is fully derived in closed-form. By construction,
the said density-matrix is parameter-free but not N-representable, owing to a
series of approximations used in the Ragot-Cortona approach. However, the
resulting density-matrix is shown to have formally correct short- and
long-range expansions. Furthermore, its momentum-space counterpart
qualitatively agrees with known parameterized momentum distributions except at
small momenta, where the disagreement reflects the non-representability of the
model and restricts to a small fraction of the slowest electrons only.
