IMPURITY EFFECTS ON ADHESION - NB, C, O, B, AND S AT A MO/MOSI2 INTERFACE

We report a quantum-mechanical calculation of impurity effects on adhesion between two materials. Adhesive properties of the Mo(001)/MoSi2(001) heterophase inter-face with and without monolayers of C, 0, B, S, and Nb impurities are calculated using a first-principles local-density-functional approach. Adhesive energies, peak interfacial strengths, and bonding characteristics are found to be strongly dependent upon impurity-atom type. The interfacial spacings increase in proportion to impurity covalent radii. All of the impurities were found to decrease the Mo/MoSi2 adhesive energy, with S lowering it by approximately a factor of 2. The substitutional impurities S and Nb decrease the peak interfacial strength, while the interstitial impurities C, 0, and B increase it. Our results are discussed in terms of experimental results on impurity effects in adhesion and embrittlement in other metallic systems.