Comprehensive understanding of size-, shape-, and composition-dependent polarizabilities of SimCn (m, n = 1-4) clusters

Abstract

We theoretically investigate the size-, shape-, and composition-dependent polarizabilities of the SimCn (m, n = 1 - 4) clusters by using the density functional based coupled perturbed Hartree-Fock method. The size-dependence of the polarizabilities of the SimCn (m, n = 1 - 4) clusters is more complicated than that of pure Sim and Cn (m, n = 1 - 8) clusters because for a given cluster size the heteroatomic clusters have more isomers than the homoatomic ones. For the shape-dependence, we consider three kinds of shape, linear (chain), prolate, and compact. For most clusters, we can clearly observe orders of {\alpha}(linear) > {\alpha}(prolate) and {\alpha}(prolate) > {\alpha}(compact) for a given composition. The composition-dependence of polarizabilities reveals that the linear clusters have an obvious larger polarizability than both the prolate and the compact clusters especially for a given m/n value. The shape effect makes a main contribution to determine the size of the polarizability. To understand the size of polarizability and the evolution of polarizability, we have tried many factors, such as the energy gap and binding energy, and defined a new parameter ({\Delta}q) that characterizes the redistribution of charge in cluster. We find that both the binding energy and the {\Delta}q are more available than the energy gap for reflecting the evolution of polarizabilities provided that both the cluster shape and one of the components in cluster are fixed. The correlation between the polarizability and the energy gap is poor, in agreement with the previous results.