Electronic Properties of Surfaces of Transition Metal Refractory Carbides and Nitrides

Electronic structure of hexagonal Ti3AlC2 and Ti3AlN2

“…Taking into account the layered structure of the hexagonal phases, a formal analogy can be drawn between the evolution of separate types of bonds (covalent and metallic) for nonequivalent titanium atoms, for example, in Ti 3 AlC 2 and in the proximity of the polar (111) face of cubic TiC (see ref. 20). In both cases, the weakening of the covalent bond Ti-C [for Ti(1) atoms of the alumocarbide or Ti atoms of the outer monolayer of the (111) face of TiC] considerably strengthens the metallicity of the bond as a consequence of redistribution of electrons between the subbands of Ti 3d-C 2p (p-d covalent bond) and Ti 3d, 4s (d-d metallic bond) states.…”

Electronic Properties and Chemical Bonding of Orthorhombic Chromium Carbide

“…The catalytic properties have motivated extensive studies on electronic [8][9][10][11] and structural properties in TMC bulk and surfaces [12][13][14][15][16][17][18] in order to understand from a microscopic point of view, which factors are responsible for the enhancement of the catalytic properties and the role played by the addition of carbon atoms to transition metals. NaCl-type structure compounds from the fourth and fifth group TMC have been the subject of extensive investigations on the electronic structure, and some similarities were found for this class of compounds such as the overlap between valence and conduction bands [9,10] and a strong hybridization of the non-metal p orbitals and the metal d orbitals [10,11,18].…”