Doping-induced structure and property variations in alkali-cluster halides: Li 13 F & Li 13 F 2

Abstract

Thirteen-atom lithium cluster mono- and di-fluorides are investigated at a DFT level of theory in both neutral and ionic states. The original shape of the metal moiety undergoes a spectrum of transformations for different spin multiplicities and charges (and relative locations of F atoms in di-fluorides), though in most cases preserving the original pattern of Li-Li bonds. There exists a series of Li₁₃F₂ isomers originating from (higher-energy) closed-shell Li₁₃F with the metal-moiety compressed along the system axis, which represent the lowest-energy states of the clusters. The “compressed” Li₁₃F isomer shows unusual charge-layers in the direction from the F atom. Natural-charge distributions exhibit always negative central Li atom of the Li₁₃ moiety strongly polarized by the fluorines, the value of the charge on Li_central changing oppositely to the overall charge of the system. Extra charges in cluster ions concentrate entirely on the metal moiety, making it an “extreme superhalogen” in the anionic system. Addition of the F atoms to Li₁₃ affects the electron affinity and ionization energy of the system moderately for the 1st and very weakly for the 2nd fluorine.