Electronic Structure of Refractory Carbides and Nitrides

Abstract

This book presents a systematic description of the electronic and physico-chemical properties of transition-metal carbides and nitrides. This is the first book devoted to the theoretical modelling of refractory carbides and nitrides and alloys based on them. It makes use of computational methods to calculate their spectroscopic, electric, magnetic, superconducting, thermodynamical and mechanical properties. Calculated results on the electronic band structure of ideal binary transition metal carbides and nitrides are presented, and the influence of crystal lattice defects, vacancies and impurities are studied in detail. Data available on chemical bonding and the properties of multi-component carbide- and nitride-based alloys, as well as their surface electronic structure, are described and compared with those of bulk crystals.

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

“…The transition metal compounds MX (M denotes a transition metal element and X denotes one of the non--metallic elements C, N or O) have attracted attention during last decade because of their high hardness, high melting point, wear and corrosion resistance [1][2][3][4][5][6][7][8][9]. The investigation of the behavior of transition metal compounds under high pressure is very important because of two reasons, namely the interests in an antiferromagnetic Mott type insulator in solid state physics and their roles in the interior of the earth [2].…”

“…In the electronic industry they are important as electric contact, diffusion barriers, buffer layer etc. In the last few years there has been an increased awareness in scandium, yttrium and lanthanum nitrides due to phase transition and their semiconducting properties [4][5][6][7][8][9]. The exchange and correlation effects were treated using the generalized gradient approximation (GGA) in case of yttrium nitride (YN) by Stampfl et al [8].…”

Physical Properties of the NbC Carbide

“…The pd σ bonds are very strong and highly directional and are responsible for the high hardness and high melting points. On the other hand, the dd π bonds, although with little contribution to the cohesion [38], are responsible for the observed transport properties (electric and thermal conductivity). It should be noted that there is also some charge transfer of the metallic electrons to the carbon atom, which gives an ionic characteristic to the bonding.…”

“…This fact explains the observed physical properties: high hardness and high melting points are properties typical of solids with ionic or covalent bonding, while thermal and electrical conductivity are characteristics of metallic bonding. The electronic structure of the transition metal carbides was extensively studied in [38] and in several other papers [39][40][41][42]. It is firmly established in the literature that the main characteristic of the chemical bonding in transition metal carbides is a covalent bonding with hybridization of the 2p orbitals of the carbon atoms and d orbitals of the metallic atom [38].…”

“…It should be noted that there is also some charge transfer of the metallic electrons to the carbon atom, which gives an ionic characteristic to the bonding. In the Nb 2 C carbide, the metallic bonding is more important and contribute more to the solid cohesion [38].…”