Theoretical Studies Of The Structures And Stabilities On Silver Clusters

Coinage mental (Au, Ag, Cu) clusters and nanoparticles have been received a great deal of attention, especially silver clusters, which are the focus of numerous investigations since they play important roles in photography, catalytic processes, novel electronic materials, surface science, and mental alloy clusters. It is well known that geometrical structures of clusters determine their special physical and chemical properties. The unique physical and chemical properties of silver clusters have been received a great deal of attention. It is well known that clusters structures and growth pattern play important roles in their properties. Thus, subjects of many investigations are searching for isomers of silver clusters, using various theoretical and experimental approaches. This study use the genetic algorithm (GA) coupled with a TB potential of Ag to search for low-energy candidates of Ag clusters. A further systematical investigation of medium-sized silver clusters Agvn (v =±1, 0; n = 21-29) was performened by using density functional theory with Perdew-Wang generalized-gradient approximation. The relative stabilities, the ionization potentials and electronic affinities of silver clusters have been analyzed. Moreover, combining with available experimental data, we investigated ionization potentials and electronic affinities. The main conclusions as following:1. For medium-sized silver clusters, the most stable isomer of neutral and ionic clusters is different. The neutral clusters show their growth pattern as follow: Ag21-23 prefer icosahedral or double-icosahedral core structures. However, Ag_n (n = 24-27) favor a bulk-like fcc stacking motif. Ag28 and Ag29 have a disclination axis. However, the ionic clusters display different stacking pattern. The reason may be that an extra electron has large effect on silver clusters growth evolving for the sized we studied.2. The analysis of relative stabilities for Agvn (v =±1, 0; n = 21-29) include three aspects: binding energies (Eb) per atom, second differences in energies (Δ2E), HOMO-LUMO gaps (ΔEH-L). The calculations show that neutral clusters Ag_n (n = 22, 24, 26), cationic clusters Ag n? (n = 21, 23, 25) and anionic clusters Ag ?n (n = 23, 25) both energetic stability and reactive stability are larger than their neighbors.3. This paper performed a systematical investigation on ionization potentials (IPs) and electronic affinities (EAs) for clusters Ag_n (n = 4-29). The general tendency of our calculations is in line with experimental results. Our results manifest that Ag_n (n = 22, 24, 26) have high value of IP and low values of EA, which reflects the relative electronic stabilities of these clusters. Electronic occupations around HOMO shells of silver clusters indicate neutral clusters Ag22, Ag24, Ag26, cationic clusters Ag 2?1, Ag 2?5 , and anionic clusters Ag 2?3 , Ag 2?5 have full-filled electronic structures, but Ag 2?3 has half filled electronic structure. This is in agreement with our analysis of relative stabilities.