THE ELECTRONIC-STRUCTURE OF TERNARY TRANS ITION-METAL PNICTIDES .1. ALB2-VARIANTS

The electronic structure and bonding of some ternary AlB2-type compoun ds AMX (A=2a-, X=5b-element, M=transition metal) were studied by means of Extended-Huckel and TB-LMTO-ASA calculations. Previous geometric s tability criteria of the AlB2 structure have been extended, and reason s for some structural peculiarities and distortions are given. A simpl e orbital interaction scheme based on local symmetry is used as starti ng point to investigate the electronic properties of these compounds, whereas the band structures of the ZrBeSi-type SrPdAs and the Peierls- distorted variants CaPdAs and BaPdP are described in more detail. The results of calculations and resistivity measurements are discussed wit hin the scope of Zintl's concept under consideration of the transition metal d-orbitals. It turns out that these solids can be described as metallic Zintl compounds.