The competition between chemical bonding and magnetism in the adsorption of atomic Ni on MgO(100)

The present study is devoted to atomic adsorption of Ni on MgO (100) surfac e and focuses on the magnetic moment of adsorbed atomic Ni in the initial p hase of metal deposition. Both cluster and periodic slab models lead to the same description, i.e., they show an almost degeneracy of the magnetic and nonmagnetic states. However, the total energy related properties are stron gly dependent on the computational method chosen. At variance with the larg e difference for the calculated heats of adsorption, the optimized values f or the Ni-O distances are remarkably close: 1.8-1.9 Angstrom for the single t state and larger than 2 Angstrom for the triplet. The paper also presents a detailed analysis of the problems connected to the definition of a prope r reference atomic energy in density functional theory approaches. (C) 2001 American Institute of Physics.