Stoichiometric interfaces of Al and Ag with Al2O3

Atomic geometries and adhesive energetics as computed from first principles are presented for stoichiometric Al(111)/Al2O3(0001) and Ag(111)/Al2O3(0001) interfaces and for the Al2O3(0001) surface. At both the interfaces and the alumina surface we found substantial interplanar relaxations within the alumina. We found the Al2O3(0001) surface energy to be 2150 mJ/m(2), in reasonable agreement with earlier results. Interfacial energies varied only 10-15% over the 3 primary sites we investigated for each metal/alumina combination. For Al/Al2O3, we found the metal equilibrium configuration to be atop Al atoms of the alumina, with a work of adhesion of 1078 mJ/m(2). For Ag/Al2O3, the work of adhesion is determined to be 672 mJ/m(2), and we found the Ag atoms to be in the (3-fold oxygen) hollow sites. These works of adhesion appear to be reasonably consistent with experimental data for solid Al or Ag on Al2O3, but allowance for nonstoichiometry in the interface (work in progress) may be important for this quantity. Finally, we discuss the accuracy of improved exchange-correlation potential approximations. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.