The energetics of an Au adatom and Au N clusters (N=2 - 6) supported on pristine and reduced MgO(100) surfaces is analyzed using an all-electron full-potential density functional theory approach. A hierarchy of exchange-correlation functional approximations is employed, ranging from the generalized gradient approximation [Perdew-Burke-Ernzerhof (PBE), revised PBE (RPBE)] to hybrid functionals [PBE0, Heyd-Scuseria-Ernzerhof (HSE06)] to exact exchange plus correlation in the random phase approximation (EX-cRPA/cRPA+). The analysis of different terms in the electronic Hamiltonian, contributing to calculated adhesion energies (E adh) for the Au adatom, shows that reducing the self-interaction error leads to smaller E adh values. On the contrary, the energy barriers for diffusion of an Au adatom at the pristine surface significantly increase. For Au N clusters (N>1), dispersion effects, not accounted for by the generalized gradient approximation or hybrid functionals, start to make an increasingly important contribution to the adhesion energy.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 4 Apr 2012|