Adhesion, atomic structure and bonding variation in TiN/VN interface by chemical segregations

Introduction of alloying elements often alters properties of materials. In the technologically significant multilayered superlattice
coatings, interfaces are known to play a key role in the deformation mechanisms, especially in the phenomenon of interfaceinduced
superhardness at nanoscale. Here, we elucidate, by first-principles calculations, atomic structure of TiN/VN interface
and its relationship to adhesion upon introducing Cr, Mo, Ta, Y, Al, Nb, Zr, and Sc, the very commonly occurring alloying elements
in the coating. We find that the elements Cr, Mo, Ta, Y weaken substantially interfacial adhesion, whereas the others modify
adhesion only slightly. The bond length, charge transfer, and interactions between atoms at interface are found to be the key
factors to understanding the origin of shift in properties in the coatings with the chemical alloying. Using several methods of
analysis, we have clarified electronic mechanism behind the variation induced by alloying elements and determined the
interfacial bonding nature to be mainly ionic with a certain degree of covalency. The theoretical calculations presented provide
insight into the complex electronic properties of the TiN/VN interfaces with alloying elements. Our findings help enhance
performances of the multilayered coatings for wide-ranging applications.