Adsorption properties of two-dimensional NaCl: A density functional theory study of the interaction of Co, Ag, and Au atoms with NaCl/Au(111) ultrathin films

Recent experiments have shown that Co atoms deposited on NaCl/Au(111) ultrathin films give rise to spontaneous substitutional doping of the NaCl layer (Li et al. Phys. Rev. Left. 2014, 112, 026102). In this work, the interaction of Co atoms deposited on NaCl/Au(111) films is investigated by means of density functional theory calculations. Co atoms have been adsorbed on various sites of the surface of unsupported and supported two- and three-layer NaCl films; incorporation of the Co atoms in interstitial positions or replacement of Na and Cl lattice ions has also been investigated. The Co adsorption properties are compared with those of Ag and Au atoms. We found that all metal atoms interact strongly with NaCl/Au(111) films, giving rise to large structural distortions of the insulating layer. Co, Ag, or Au incorporation in interstitial positions between the first and second NaCl layers is thermodynamically preferred over adsorption on surface sites. The results show the reactivity of NaCl with Co is higher than that with Ag and Au and the large structural flexibility of ultrathin films of insulating materials grown on a metal support compared to the unsupported NaCl counterpart.