Predicting novel atomic structure of the lowest-energy Fe _n P_13–n (n = 0–13) clusters: A new parameter for characterizing chemical stability

Abstract

In this study, a series of novel atomic structure of lowest-energy FenP13-n (n=0-13) clusters via density functional theory (DFT) calculations and an unbiased structure search using Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) code. Our research results show that the global minimum geometry structure of neutral Fe13-nPn (n=0–6) clusters tend to form cage structures but the lowest-energy Fe13-nPn (n=7– 13) clusters are gradually evolution from a cage structure to a chain shape geometric structure. Their geometric structure should responsible for the raise of binding energy from Fe7P6 to P13 clusters rather than chemical components. This is completely different from a linear relation of the binding energy with chemical components in our previous research for Cu n Zr13-n (n=3–10) clusters (Yuanqi Jiang, et.al. Journal of Molecular Liquids,343,117603). Hence, in order to characterize the global chemical stability of target cluster, we proposed a new parameter (jyq= $\frac{\eta }{\chi }$) that the chemical hardness of isolated cluster is used to be divided by its electronegativity. One of the biggest advantages of this parameter is successful coupling the ability of a resistance to redistribution of electrons and the ability to attract electrons from other system (such as atom, molecular or metallic clusters). Moreover, it is found that the P13 cluster shows typical insulator characteristics but the Fe12P1 shows typical conductor characteristics, which phenomena can be attributed to the remarkable delocalized and localized electrons in Fe12P1 and P13, respectively. In terms of nearly-free-electron mode, we also found that the number of electrons on Femi level (N(E f)) are obviously tended to toward a lower value when Fe was replaced gradually with P from Fe13 to P13, and a non-magnetic can be observed in Fe13, Fe2P11, Fe1P12 and P13 that mainly because their perfect symmetrical between spin-up and spin-down of density of states of electronic.