Atomic structure and adhesion of theNb(001)/α-Nb5Si3(001) interface: a first-principles study

Abstract

The density functional calculations have been performed to study the Nb(001) andα-Nb5Si3(001) surfaces as well as the interface properties ofNb(001)/α-Nb5Si3(001). The surface energy of the Nb(001) surface is about2.25 J m − 2. The calculated cleavageenergies of bulk Nb5Si3 are 5.103 J m − 2 and 5.787 J m − 2 along (001) planes with the breaking of Nb–Si and Nb–NbSi bonds, respectively. For theNb(001)/α-Nb5Si3(001) models, the Nb atoms in the interface region initially belonging to bodycentered cubic metal Nb are twisted to the position of the Nb atom layer inNb5Si3 and the interlayer distance is similar to that of bulkNb5Si3 after being fully relaxed. The ideal work of adhesion of theNb(001)/Nb5Si3(001) interface is calculated and compared to those of bulk Nb andNb5Si3. The results showthat the bulk Nb5Si3 has the largest work of adhesion, the bcc Nb ranks second and the interface ranks last.Moreover, the Nb–Si bond is weaker than Nb–NbSi and Nb–Nb bonds in the interface,which means that the Nb–Si bond in the interface is the most possible site for themicro-crack generation when the stress is applied quasi-statically along the [001]direction. The densities of states, Mulliken population and overlap population of theNb(001)/α-Nb5Si3(001) interface are also analyzed.