LMTO BAND-STRUCTURE CALCULATIONS OF THCR2SI2-TYPE TRANSITION-METAL COMPOUNDS

The electronic structures of ThCr2Si2-type compounds mere studied by m eans of self-consistent LMTO hand structure calculations. Different bo nding interactions in SrRh2P2 are analyzed and their dependence on the electron count are discussed in terms of the formal substitution of e lements. The overall bonding situation can be characterized as an inte rplay between covalent, metallic, and ionic interactions, although met al-metal bonding plays an important role. Particularly, the evolution of the interlayer bonding between the nonmetal atoms by changing the t ransition metal is examined in more detail. It turns out that the shor tening of the interlayer bonds by filling the d shell of the transitio n metal is due to an increasing occupation of nonmetal bonding states which are pushed up to the vicinity of the Fermi level by antibonding metal-nonmetal interactions. The hand structures of superconducting Eu Ni2B2C and nonsuperconducting SrRh2P2 are compared and their similarit ies are pointed out. A van Hove singularity, generated by metal-metal interaction, coincides with the Fermi level in LuNi2B2C and lies about 0.2 eV higher in SrRh2P2. By doping, it should be possible to induce superconductivity in SrRh2P2 and related compounds. (C) 1997 Academic Press.