Density functional prediction of a magnetic ground state of UFeSi

Density functional (DF) electronic structure calculations for UFeX (X=Si, G el compounds were performed using fully relativistic optimized linear combi nation of atomic orbitals (OLCAO), relativistic general potential linear au gmented plane wave (LAPW) and scalar relativistic augmented sphere wave (AS W) methods. The Sf-states of uranium were assumed itinerant and treated as band states. We confirm the experimental observation that UFeGe is a parama gnet. On the other hand, our extensive DF calculations including the fixed- spin-moment method predict an instability of the paramagnetic state of UFeS i in the orthorhombic TiNiSi structure. Since both UFeSi and UFeGe are isoe lectronic with respect to the number of valence electrons the actual ground states result from a subtle interplay between the band filling of the free electron background (s-, p-, and U-d electrons) and the iron bonding bands on one side and the covalency (hybridization) between bonding predominantl y 3d states of iron and antibonding predominantly 5f-states of uranium on t he other side. (C) 2001 Elsevier Science B.V. All rights reserved.