Siqi Shi

First-principles study on the adhesion nature of the α-Al2O3(0001)/Ni(111) interface

First-principles calculations of the α-Al2O3(0001)/Ni(111) interface have been performed, and are compared with our previous results of the α-Al2O3(0001)/Cu(111) interface (Yang et al 2004 Phil. Mag. Lett. 84 425, Yang et al 2005 Phil. Mag. 85 2961). Interface models where the Ni atoms are located on top of the interface O atoms have been examined. For the O-terminated interface, the adhesion is caused by the strong O-2p/Ni-3d orbital hybridization and ionic interactions. For the Al-terminated interface, the adhesion originates from the image-like electrostatic and Ni–Al hybridization interactions. Charge transfer occurs from Al2O3 to Ni, which is opposite to that in the O-terminated interface. The degree of orbital hybridization and adhesive energies are more significant for the Al2O3/Ni interfaces than for the Al2O3/Cu interfaces, because of more reactivity of Ni.

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi(5) hydrogen storage alloy. At low coverages, CO favors adsorption on Ni-Ni bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for Ni-Ni-CO bridge adsorption than that for Ni-CO on-top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi(5) (001) surface is analyzed in detail.