Stabilization of monovalent and mixed valent cations in snnom clusters and predictive applications – First Principles Calculations

Abstract

In this work, the stoichiometric dependent structural stability and electronic properties of tin oxide nanoclusters (Sn_nO_m, n = 1 - 6; m = 1 - 2n) is explored  by employing first principles density functional calculations. The results show that stable Sn_nO_n (m = n) clusters found to have large binding energy, in  given n series, due to having high structural symmetry, large energy gap between highest occupied molecular orbital and lowest unoccupied molecular  orbital (HOMO-LUMO gap), and univalent charge distributions among Sn and oxygen atoms. On the other hand, stable Sn_nO2_n clusters have possessed  with mixed charge states of Sn²⁺ and Sn⁴⁺ ions. The presence of both Sn²⁺ and Sn⁴⁺ ions in these clusters originates weakly adsorbed O₂ molecule on  these clusters, which is quite consistent with earlier experimental work. Interestingly, the structure of some of large sized stable clusters is observed to  be resemblance with fused form of two stable isomers. By calculating chemical  hardness of Sn_nO_m clusters, we also show that SnnOn clusters are   chemically inert and they can be used for optoelectronic devices  owing to presence of lone pair Sn2+ ions. Whereas, in Sn_nO_m  clusters (m > n), both Sn²⁺  and Sn⁴⁺ ions are presented, thus, they  can be used for catalytic or sensing applications.