Electronic structure and Fermi surfaces of transition metal carbides with rocksaltstructure

Abstract

First-principles calculations were carried out to investigate the structural and electronicproperties of the metal carbides FeC, CoC, NiC, and PtC in the rocksalt structure. Thefull-potential linearized augmented-plane wave (FP-LAPW) method was used in theframework of the density-functional theory with the generalized gradient approximation(GGA) for the exchange–correlation potential. Ground state properties are determinedand compared with available experimental data. The energy band structures,densities of states, and Fermi surface structures are obtained, which show that thesecompounds are metallic like the conventional transition metal carbides. Thereis an extensive hybridization between the metal-d and C-2p states for all thestudied carbides, which can form bonding and antibonding states. From FeC toPtC a band narrowing for the hybridized metal-d and C-2p states near to theFermi level takes place, which is expected to lead to smaller interactions betweenadjacent atoms. The largest bulk modulus of FeC is expected to be associatedwith the behavior of valence electrons near the Fermi level, i.e. a higher degree ofhybridization between p–d states that are responsible for the chemical bonding results instrengthened interactions. The decrease in the number of bonding orbitals or decrease inmetallic valence with the increase in number of 3d electrons from FeC to PtCprovides a mechanism for weaker interactions due to the filling of antibonding bands.