Thermochemical Properties and Growth Mechanism of the Ag-Doped Germanium Clusters, AgGe with = 1-13 and λ = -1, 0, and +1.

A systematic investigation of the silver-doped germanium clusters AgGe with = 1-13 in the neutral, anionic, and cationic states is performed using the unbiased global search technique combined with a double-density functional scheme. The lowest-energy minima of the clusters are identified based on calculated energies and measured photoelectron spectra (PES). Total atomization energies and thermochemical properties such as electron affinity (EA), ionization potential (IP), binding energy, hardness, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap are obtained and compared with those of pure germanium clusters. For neutral and anionic clusters, although the most stable structures are inconsistent when = 7-10, their structure patterns have an exohedral structure except for = 12, which is a highly symmetrical endohedral configuration. For the cationic state, the most stable structures are attaching structures (in which an Ag atom is adsorbed on the Ge cluster or a Ge atom is adsorbed on the AgGe cluster) at = 1-12, and when = 13, the cage configuration is formed. The analyses of binding energy indicate that doping of an Ag atom into the neutral and charged Ge clusters decreases their stability. The theoretical EAs of AgGe clusters agree with the experimental values. The IP of neutral Ge clusters is decreasing when doped with an Ag atom. The chemical activity of AgGe is analyzed through HOMO-LUMO gaps and hardness, and the variant trend of both versus cluster size is slightly different. The accuracy of the theoretical analyses in this paper is demonstrated successfully by the agreement between simulated and experimental results such as PES, IP, EA, and binding energy.