Conduction band of IVa and Va subgroup transition metal monocarbides (I)

Abstract

Dedicated to Prof. Dr. Dr. h.c. P. GORLICH, on the occasion of his 65th birthday Basing on the general conceptions of the band structure of stoichiometric IVa subgroup transition metal monocarbides and assuming two types of atomic interactions a conduction band model for nonstoichiometric carbides has been elaborated which takes into account the vacancies in the carbon sublattice. It is assumed that the formation of vacancies is accompanied by the appearance of local electronic levels in the vicinity of the Fermi level of stoichiometric carbide which, in the case of high concentrations of C-vacancies, form a subband of unscreened Me-Me bonds. This results in a filling of the Me-C band, a shift of the Fermi level into the Me-Me band, followed by an increase of the electron density of states and an increase of the Ferrni level. The increasing density of states leads to an increase in the magnetic susceptibility

Ordering and Magnetic Susceptibility of Non-Stoichiometric Hafnium Carbide

“…As the composition of group IV transition metal carbides deviates from stoichiometry the Fermi level displaces from the bottom of the high-energy M±M conduction band to the region of higher energies. The density of electron states N(E F ) increases at the same time [21] and, as a consequence, the quantity c À p 0 increases too. According to [22], the collectivized electron effective mass, m * , is small if the energy band is nearly empty.…”