Validity of the Anderson and Hubbard Models for the Description of Metallic Ce and Cerium Heavy Fermion Compounds

The importance of the inclusion of inter-site f-f hybridization in electron structure calculations for metallic Ce and cerium heavy fermion compounds was studied. We demonstrate that for heavy-fermion systems such as cerium compound CeCu(2)Si(2) f-f hybridization can be neglected and Anderson model application is well justified. On another hand for cerium metal f-f hybridization is strong enough to provide the contribution to hybridization function comparable to hybridization between 4f and itinerant electrons. We argue that in the case of Ce only the most general Hamiltonian combining the Hubbard and Anderson models should be used.