Double occupancy of theforbital in the Anderson model for Ce compounds

The Anderson model at zero temperature is studied as a function of the f-level position ${\varepsilon }_f$ and the f-level–conduction-electron hopping matrix element V. The f-f Coulomb interaction U is assumed to be finite, and double occupancy of the f level is taken into account. For a large value of the f-level degeneracy $N_f$, there is an important asymmetry between $f^0$ and $f^2$ configurations. Even for ‘‘symmetric’’ parameters, 2${\varepsilon }_f$+U=2${\varepsilon }_F$=0, the $f^2$ weight is much larger than the $f^0$ weight if V is small. The effect of this asymmetry on other properties is studied for $N_f$→∞. The static susceptibility is primarily determined by