Theoretical Study Of The COLi_n And M_kF_2k-1⁺（M=Mg,Ca;k=2,3） Clusters

This paper theoretically designs COLi_nclusters and M_kF_2k-1⁺clusters,and systematically study were carried on with respect to their geometries,distribution of charge, HOMO-LOMO gaps and electron affinities. Themain contribution is as follows,（1） A theoretical study was carried out about the complexes composedof carbon monoxide and small lithium clusters, namely COLi₂, COLi₄,COLi₅, COLi₈, COLi₆⁺, and COLi₇⁺. The complexation of carbonmonoxide with Li2is found to be endothermic and not spontaneous. Asfor Li4and Li₅⁺, they can only reduce CO to single bond length. Bycomparison with the N₂-Lincomplexes where a minimum of eight lithiumatoms are needed to cleave the triple bonded nitrogen completely, the Lincluster behaves more efficiently in activating the CO molecule becausethe Li6cluster is sufficient to cleave the C-O triple bond in a highlyexothermic way. Besides, the degree of reduction of CO graduallyincreases with Linbecoming larger, and the Li₇⁺and Li8clusters cancleave the C-O triple bond to greater extent than Li₆does. Due to theability of lithium clusters to cleave the N-N and C-O triple bonds ineffective ways, they offer a promising approach to activate other strongchemical bonds. （2） A series of M_kF2k-1⁺（M=Mg, Ca; k=2,3） cations had beentheoretically investigated. Thirteen out of seventeen cations wereidentified as superalkali cations because of their lower vertical electronaffinities （EAvert） of3.258⁵.335eV than the ionization potential of Liatom. These species also exhibit considerably large HOMO-LUMO gapsand binding energies. It was proposed that the alkaline-earth atoms couldpartner with halogens to construct low EA cations, which may add newcandidates to the superalkali family.We hope that the principles obtained from this study may, in the future,provide a useful guidance for superatom researches and new materialsdesigning.