Competition between Kondo and RKKY exchange couplings in Pu(1-x)Am(x) alloys: Density functional theory with static Hartree-Fock and dynamic Hubbard-I approximations

Abstract

To clarify the role of the Kondo effect in screening local magnetic moments Of Plutonium 5f electrons as well as its competition to the RKKY interactions, we use a combination of density functional theory with static Hartree-Fock and dynamic Hubbard-I approximations to calculate the strength of both the Kondo exchange, J(K), and of the RKKY exchange, J(RKKY), couplings for Pu1-xAmx system as a function of x. We find that within the range 0 <= x <= 1/2, J(K) increases despite that the atomic volume gets larger with the Am doping due to unexpected enhancement of hybridization between f and conduction electrons in the vicinity of the Fermi level. At the same time, the RKKY exchange is shown to reduce smoothly with increasing x. Our results imply that the Kondo effect should be robust against the increase in interatomic spacing of this alloy, which places this system away from quantum critical behavior.