A dispersion-corrected DFT insight into the structural, electronic and CH4 adsorption properties of small tin-oxide clusters.

The main goal of this paper is to investigate the structural and electronic properties of small tin-oxide clusters, Sn x O y (x = 2–6), before and after methane (CH 4 ) physisorption. To this end, we employ the dispersion-corrected density functional theory (DFT-D2). At first, we demonstrate the relative binding stability of Sn x O y clusters with a fixed number of tin atoms via analysis of their binding energy per atom and second-order energy differences. Our results show that the highest relative stability occurs at y = 2, y = 3, y = 4, y = 6 and y = 8 for Sn 2 O y , Sn 3 O y , Sn 4 O y , Sn 5 O y and Sn 6 O y clusters, respectively. Furthermore, with the cluster size increasing, the ring-shape to cube-like structural crossover is occurred. The higher average coordination and total number of bonds in cube-like clusters make their interatomic bonds weaker and longer. On the other hand, the cube-like clusters, in comparison with ring-shape ones, possess higher chemical potential and lower chemical hardness that lead to their more chemical reactivity. We then proceed to study the CH 4 adsorption properties of the resulted most stable clusters. The lowest-energy structures of CH 4 -adsorbed clusters have been found by comparing the adsorption energy of different configurations. It is found that Van der Waals interactions lead to exothermic physisorption of CH 4 on each tin-oxide cluster with the adsorption energy ranging from −101 to −191 meV. In addition, upon CH 4 adsorption on Sn x O y clusters, the energy gap is decreased which shows an enhancement in the conductivity of the clusters. As a result, the CH 4 physisorption ability of these small studied tin-oxide clusters provides their application feasibility as the low-temperature CH 4 gas sensors. [ABSTRACT FROM AUTHOR]