Bonding at metal-ceramic interfaces; ab initio density-functional calculations for Ti and Ag on MgO.

Schonberger U., Andersen O.K., Methfessel M.

The authors have performed ab initio local density-functional calculations of the equilibrium geometries, force constants, interface energies and works of adhesion for lattice-matched interfaces between rocksalt-structured MgO and a FCC transition or noble metal (M=Ti or Ag). The interfaces had (001)M//(001)MgO and (100)M//(100)MgO. The authors used the full-potential LMTO method. Both Ti and Ag are found to bind on top of oxygen. The interface force constants are 3-4 times larger for Ti mod MgO than for Ag mod MgO. These, as well as the M-O distances (2.18 AA for Ti-O and 2.5 AA for Ag-O), indicate that the Ti-O bonding is predominantly covalent with the Ti oxidation state less than +1, and that the Ag-bonding is predominantly ionic, as in Ag2O, with the Ag oxidation state close to +1. The calculated interface energies are both 0.8 eV/M mod MgO and the interface adhesions are, respectively, 1.2 eV/Ti mod MgO and 0.9 eV/Ag mod MgO. The calculated (strained) surface energies are, respectively, 1.1 eV/Ti mod , 0.7 eV/Ag mod and 1.0 eV/MgO mod .

Acta Metallurgica et Materialia, 40 S1-10, 1992.

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