Molecular-orbital model for metal-sapphire interfacial strength

Abstract
Self‐consistent‐field X‐Alpha scattered‐wave cluster molecular‐orbital models have been constructed for transition and noble metals (Fe, Ni, Cu, and Ag) in contact with a sapphire (Al2O3) surface. It is found that a chemical bond is established between the metal d‐orbital electrons and the nonbonding 2p‐orbital electrons of the oxygen anions on the Al2O3 surface. An increasing number of occupied metal‐sapphire antibonding molecular orbitals explains qualitatively the observed decrease of contact shear strength through the series Fe, Ni, Cu, and Ag.