  We show that incorporation of strong electron correlations into the Kohn-Sham
scheme of band structure calculations leads to a modification of the standard
model of the lanthanides and that this procedure removes the existing
discrepancy between theory and experiment concerning the ground state
properties. Within the picture suggested, part of the upper Hubbard $f$-band is
occupied due to conduction band-$f$-mixing interaction (that is renormalized
due to correlations) and this contributes to the cohesive energy of the
crystal. The lower Hubbard band has zero width and describes fermionic
excitations in the shell of localized $f$-s. Fully self-consistent calculations
(with respect to both charge density and many-electron population numbers of
the $f$-shell) of the equilibrium volume $V_0$ and the bulk modulus of selected
lanthanides have been performed and a good agreement is obtained.
