EFFECT OF COMPOSITION ON THE ANDERSON HYBRIDIZATION IN TERNARY CUBIC ALLOYS OF CE

The cubic compounds of Ce with Zn, Ag and Cd are considered to behave as Kondo lattices depending on applied pressure or alloying. In partic ular their magnetic behaviour is ascribed to the possible competition between the RKKY interaction and the Kondo effect. We calculate the hy bridisation width DELTA of the Anderson model for the two ternary cubi c compounds CeCd1-xAgx, CeCd1-xZnx. This quantity determines, along wi th the position E(f) and correlation U of the Ce f-state, the antiferr omagnetic coupling constant J(s-f) of the Kondo Hamiltonian. We start from ab initio electronic calculations performed with the FLAPW method in the LSDA and carry out an LCAO parametrisation of the band structu re for the pure binary compounds. A virtual-crystal approximation is u sed to obtain the LCAO parameters of the ternary alloys. We cheek the accuracy of this approximation on CeCd0.5Zn0.5 by a self-consistent FL APW calculation on the supercell Ce2CdZn, finding that it is satisfact ory for the present purposes. We find that DELTA, in the whole concent ration range, is affected quantitatively much more by substitution of Cd by Ag than by Zn-isovalent to Cd-, although the latter one induces a larger volume reduction. Moreover, the DELTA behaviour in CeCd1-xZnx , contrasts with the expected volume dependence. This shows that elect ronic effects may be more effective than electronic pressure alone (vo lume effects) in determining the Kondo properties of substitutional sy stems.