First-principles calculation of W/WC interface: Atomic structure, stability and electronic properties

The structural, adhesive, and electronic properties of α-W(1 1 0)/α-WC(0 0 0 1) interfaces are studied by first-principles calculation based on density functional theory (DFT). Six different W/WC interface geometries are considered in this study, including two terminations of WC(0 0 0 1) surface, and each of them involves three different stacking sequences. It is demonstrated that whatever stacking sequence is, the interfacial separations of C-terminated interfaces decrease after optimization, and the lateral movement of the interfacial W atoms will bring three nearest neighbor C atoms around it. Therefore, the C-terminated interfaces are stable geometries, and yield larger adhesion energy, Wad. Using several analytic techniques including charge density distribution and its difference, and density of states, we characterized the electronic properties and determined the interfacial bonding of W-terminated hollow-site interface to be of metallic nature while the interfacial bonding of C-terminated hollow-site interface to be of a mixed covalent-ionic nature.