Electronic Structure of Refractory Carbides and Nitrides by V. A. Gubanov

By V. A. Gubanov

This publication provides a scientific description of the digital and physico-chemical houses of transition steel carbides and nitrides. The dialogue is dedicated to the theoretical modeling of refractory carbides and nitrides and alloys in line with them, and the authors uniquely utilize computational the right way to calculate their spectroscopic, electrical, magnetic, superconducting, thermodynamical, and mechanical houses.

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Extra resources for Electronic Structure of Refractory Carbides and Nitrides

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As soon as the metal atoms in the carbides have octahedral coordination, one can break metal d states into t2g(dxy, dxz, dyz) and eg{d2z and d\ — y2) orbits. The calculations show that the eg states contribute most to the hybridisation band and the t2g states to the metal band. 1 Cubic carbides of Ti, F, Zr, Nb, Hf& Ta 21 is due to (j-hybridisation of the 2p-orbitals of the nonmetal atoms and ^-orbitals of the metal atoms. In Samsonov and Goryatchev (1977) and Zhukov, Gubanov, Ivanovsky, and Shveikin (1980) cluster models were used for the estimation of metal-metal and metal-nonmetal bonding energies in TiC, which lead to the definite conclusions on much stronger metal- nonmetal bonds.

1 Calculated and experimental0 values of some properties for transition metals and refractory carbides (LMTO calculations). 4 756 740 3621 3886 Calculated and experimental values are given in the numerator and denominator, respectively. 47 — 426 — — — 22 Hexagonal V & Nb carbides 29 are total energy calculations using MT or LMTO methods. For example, the total energies calculated by the LMTO method for the hep HfC, HfN and TaC turn out to be lower than that for the fec-phases (Zhukov, Medvedeva and Gubanov, 1989).

Calculations of overlap populations show that the Cr4p-C2p interaction, which was assigned by Nemoshkalenko et al as decisive in Cr-C bonding, turns out to be an order of magnitude less strong than the corresponding values for the Cv3d-C2p interaction. Zhukov et al (1989) calculated the band structure, lattice constants, bulk modulus, cohesive energy and the hydrostatic breakdown tension for the hypothetical CrC monocarbide and compared them with the values for TiC, VC, TiN and VN. 1. A qualitative explanation of such a behaviour based on the canonical band theory of Andersen (1975) was given in the review by Zhukov et al (1989).

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