Compton scattering study on the electronic properties of niobium carbide and niobium nitride

The electronic structure, experimental Compton profile and the chemical bon ding mechanism of niobium carbide and niobium nitride are studied on the ba sis of the band structure calculations, using a self-consistent, all-electr on, linear combination of Gaussian orbitals (LCGO) calculation based on den sity functional theory. Isotropic Compton profiles of niobium carbide have been measured, using a conventional technique based on 59.54 keV gamma-radi ation with a solid state detector. The agreement between the experimental a nd the theoretical momentum density is very good. It is shown that the anis otropies at low momentum are heavily influenced by the particular shape of the Fermi surface. The charge distributions resulting: from valence bands i n different regions of the unit cell are discussed. The limitations of the rigid band structure model are illustrated and general trends in the chemic al bonding are discussed. (C) 2000 Elsevier Science Ltd. All rights reserve d.