First-principles study of NbC/Nb interface stability and electronic structure

The NbC/Nb composite layer can be fabricated on the surface of refractory metal Nb by in-situ hot pressure diffusion method. The interface bonding, coherent mismatch and stability of the NbC/Nb microphase interface should be valued because they are important for the improvement of the properties of the composite layer. This study investigated the interactions between atoms at the NbC/Nb interface, considering the first-principles approach of density functional theory. Six interface models were constructed, and the density of states, work of adhesion, formation enthalpy, Mulliken analysis and charge density were mainly analyzed when the NbC/Nb interface was Nb terminal and C terminal respectively. The Nb(100)-NbC(001)(C) interface exhibited the lowest density of states at the Fermi energy level, the largest adhesion work (0.84 J/m(2)) and the smallest formation enthalpy. In the interface of Nb(100)-NbC(001)(C), Nb and C form a covalent bond, which has the largest number of layouts and the shortest bond length, showing strong stability that cannot be easily broken.