On the nature of noble gas – metal bond in silver aggregates

Abstract

The aim of this paper is to extend the study of the nature of the bond between noble gas to nano- and sub nanoscale silver aggregates. In the framework of DFT-PAW calculations implemented in the abinit package, we carried out a thorough investigation on the nature of the bond between the six noble gases NG (He, Ne, Ar, Kr, Xe and Rn) and numerous neutral silver aggregates Ag_n from the single atom Ag₁ to the nanoparticle Ag₁₄₇ using atoms-in-molecules (AIM) dual functional analysis,. We evaluated the impact of the silver aggregate size, the adsorption site and of the noble gas on the Ag–NG bond. Our study concluded on the favored adsorption of heavier noble gases (Kr, Xe and Rn) over that of lighter noble gases (He, Ne and Ar) on any aggregate size due to an enhanced chemical contribution in the bond. For these heavier noble gases, in accordance with studies carried out on surfaces, we noted their preferential adsorption on on-top sites rather than on hollow sites, which further evidences the chemical contribution to the bond. Moreover, the slight positive Bader charge on these heavier noble gases implies an electron transfer from the noble gas to the silver atom. Noble gas adsorption is favored on smaller, few-atom, two-dimensional clusters rather than on larger three-dimensional nanoparticles. Finally, we identified a universal power law with a unique exponent linking bond length and electronic density at the bond critical point for all aggregate sizes, noble gases and adsorption sites.