AB-INITIO PSEUDOPOTENTIAL CALCULATIONS FOR THE ELECTRONIC-STRUCTURE OF LOW-T-C LUNI2B2C AND THE RELATED COMPOUND LUNIBC

Ab initio pseudopotential calculations are performed for the electroni c structure of the low-T-c intermetallics LuNi2B2C and the related non superconducting compound LuNiBC. Electronic structures of the two comp ounds are compared in great detail, especially in terms of the Fermi s urfaces and the symmetry-decomposed density of states (DOS) near the F ermi level. The estimated electron-phonon coupling constant lambda (0. 8-1.1) from the heat-capacity data as well as from the calculated DOS at E(F) indicates that T-c of LuNi2B2C is reasonably well explained by the conventional Bardeen-Cooper-Schrieffer mechanism with intermediat e coupling strength. The relatively high T-c arises from the large DOS at the Fermi level. Absence of superconductivity in LuNiBC may be und erstood to be due to the reduced DOS at E(F). Unlike the high-T-c cupr ates, the low-T-c LuNi2B2C does not have the half-filled sigma-antibon ding bands and its electronic structure is almost three dimensional de spite the layered atomic structure.