A CALCULATION OF THE STRUCTURE AND ENERGY OF THE NB AL2O3 INTERFACE/

We have modelled the (111)(Nb)/(0001)(s)Nb/Al2O3 interface using an at omistic, static lattice simulation technique. The interaction between the metal and the oxide combines the short range interaction between t he metal atoms and the oxide ions, the Coulomb interaction between the oxide ions and the induced image charge of the metal, and the energy required to immerse the ionic cores in the metal jellium. The short ra nge interaction between the Al3+ ion and the Nb atom was found to be r epulsive, but the O2-/Nb interaction was found to be attractive at sep arations greater than 0.23 nm. As a result the lowest energy interface was found to terminate on an oxygen plane of the Al2O3; crystal, with the Nb atoms placed over the vacant sites in the Al lattice. The inte rfacial energy of this interface was calculated to be -3.6 J/m(2). As in previous work the results agree well with LDF calculations. The cal culated structure is also in good agreement with the interpretation of the HREM images of Nb films grown on the (0001) face of Al2O3 using M olecular Beam Epitaxy. Copyright (C) 1996 Acta Metallurgica Inc.