CNDO MO calculations for hydrogen atom adsorption on nickel atom clusters

CNDO molecular orbital calculations have been done for H atom interactions with various locations on (100), (110), and (111) surfaces of nickel atom clusters containing up to 10 nickel atoms. The CNDO procedure used was basically a modification of that introduced by Pople in which all molecular orbitals are doubly occupied except for the highest occupied MO which contains one electron. Equilibrium positions have been determined both with respect to distance from the surface and position on the surface. Hydrogen atoms are more stable in multicenter bonds over holes than when directly over a surface atom. The (111) surface produced the greatest binding energy. For the Ni clusters the s and p orbitals of the Ni atoms were primarily responsible for the nickel–hydrogen bonding with the d orbitals playing a relatively minor role. The adsorbed hydrogen atom carries a negative charge.