Ab initio pseudopotential calculations for the electronic structure of low-Tc LuNi2B2C and the related compound LuNiBC

Ab initio pseudopotential calculations are performed for the electronic structure of the low-Tc intermetallics LuNi2B2C and the related nonsuperconducting compound LuNiBC. Electronic structures of the two compounds are compared in great detail, especially in terms of the Fermi surfaces and the symmetry-decomposed density of states (DOS) near the Fermi level. The estimated electron-phonon coupling constant λ (0.8--1.1) from the heat-capacity data as well as from the calculated DOS at EF indicates that Tc of LuNi2B2C is reasonably well explained by the conventional Bardeen-Cooper-Schrieffer mechanism with intermediate coupling strength. The relatively high Tc arises from the large DOS at the Fermi level. Absence of superconductivity in LuNiBC may be understood to be due to the reduced DOS at EF. Unlike the high-Tc cuprates, the low-Tc LuNi2B2C does not have the half-filled σ-antibonding bands and its electronic structure is almost three dimensional despite the layered atomic structure