The nature of stability and adsorption interactions of binary Au–Li clusters with bridge adsorption structures

Abstract

Earlier findings have confirmed that CO molecules have propensities to adsorb on low-coordinated gold atoms (top sites) of Au-based clusters, which can be treated by the Blyholder model wherein the σ donation and π-back donation take place. Here, the structural features and stability of (AuLi)_n (n = 1–9) clusters were first analyzed using the GA-DFT method. The new adsorption modes, vibration frequencies and electronic interactions for Au–Li clusters with CO were investigated in detail. More excitingly, we found that CO prefers to adsorb on the bridge sites of the Au–Li clusters rather than on the top sites, which are much lower in energies than the top adsorptions, and the C–O stretching frequencies are also red-shifted. AIMD simulations show that the adsorption structures still have good thermal stability at 500 K. The density of states reveals that the electronic structures of Au–Li clusters have excellent stability for the bridge adsorptions of CO molecules. The ETS-NOCV analysis and NPA charges show that the direction of charge flow is from Au–Li clusters → CO. Our study provides an idea to elucidate the new adsorption mechanism on Au–Li clusters and the connection between the geometries and reaction properties.