First-principles investigation on the electronic property and bonding configuration of NbC (111)/NbN (111) interface

Abstract

The NbC (111)/NbN (111) interfaces were studied by first-principles calculation based on density functional theory to supply the theoretical basis for developing the novel NbC/NbN nano-multilayered film. Surface convergence calculations demonstrate that both NbC slab and NbN slab with more than thirteen atom-layers exhibit bulk-like interior feature. Thirty-six specific geometry models of NbC (111)/NbN(111) interface with different termination structures and stacking sequences were chosen. The calculated interfacial ideal work of adhesion and interfacial distance suggest that interface termination structure and stacking sequence both play the important role on influencing the interfacial stability, in which, C-terminated NbC is more inclined to join with the Nb-terminated NbN while the Nb-terminated NbC is more inclined to join with the N-terminated NbN. Moreover, for the C-N terminated and Nb-Nb terminated interfaces, the OT stacking sequence shows the highest stability, while for the C-Nb terminated and Nb-N terminated interfaces, the TL stacking sequence shows the highest stability. For the most stable C-Nb terminated and Nb-N terminated NbC (111)/NbN (111) interfaces, the atomic structure and the electronic transition from NbC to NbN are undertaken smoothly across interface. The chemical bond between the neighbor Nb atom and C or N atom in interface system shows both covalency and ionicity. Moreover, the transferred charge from Nb atom to N atom is larger than that from Nb atom to C atom, which may be the reason that Nb1-N terminated interface revealing the higher interfacial stability than C1-Nb terminated one.