Theoretical Design Two Types Of Novel Superatoms

Specific clusters,which exhibit similar chemical behaviors to atoms in the periodic table,are regarded as superatoms.In recent years,the field of superatoms has drawn numerous attention from both experimental and theoretical research groups,and a great deal of superatoms have been characterized.The research for superatoms broaden the traditional periodic table to a third dimension and make superatoms have broad development prospect and research value.In thesis,two types of novel superatoms were designed and explored.As for those superalkali cations,their geometries and electronic structure were mainly analyzed.Regarding to the hyperhalogens,it was focused on discussion of the structural features,electron detachment energies,and molecular magnetism.The main contents of this dissertation are summarized as follows:1.A new series of polynuclear superalkali cations YLi₄⁺?Y=PO₄,AsO₄,VO₄?has been characterized using ab initio methods.The central Y^3-(PO₄^3-,AsO₄^3-,VO₄^3-)acid radicals preserve their structural and electronic integrity in the first several lowest-lying isomers of YLi₄⁺.Meanwhile,the introduction of Li⁺cations can also dissociate an O^2–ion from the Y^3-groups.Besides,the AsO₄^3-group is discerned to be separated into AsO₂^–and O₂^2–fragments other than AsO₃^–and O^2–units.This is why the AsO₄Li₄⁺cation has been found to possess more diverse structures.The vertical electron affinities(EA_vert)of the YLi₄⁺cations range from 2.44 to 4.67 eV,which are low enough to validate the superalkali or pseudoalkali identity of the title species.It is also noteworthy that the YLi₄⁺conformer with T_d symmetry makes for a more even distribution of the excess positive charge,and consequently exhibits the lowest EA_vertert value of ca.2.45 eV.2.A new series of polynuclear cations MF₆Li₄⁺?M=Al,Ga,Sc?have been theoretically investigated based on density functional theory calculations.The regular octahedral MF₆ groups,although maintained their integrity,distorted to some degree upon the introduction of Li ligands.It has been found that the Li ligands prefer to occupy the bridge-or hollow-site of the MF₆ core.According to the MP2 results,the MF₆Li₄⁺cations have lower vertical electron affinities(EA_vert,2.618³.212 eV)than the threshold of 3.89 eV,verifying their superalkali identity.Besides,the MF₆Li₄⁺configurations with more dispersive Li ligands possess lower EA_vert values.More importantly,large HOMO-LUMO gaps,binding energies per atom?E_b?,and positive fragmentation energies ensure the stability of these cations.3.A series of M_kF⁺_2k-1?M=Mg,Ca;k=2,3?cations have been theoretically investigated to make a new attempt to design superalkali species.As expected,most of these cations were identified as pseudo-alkali or even superalkali cations in view of their low electron affinities?EAs?.The stability of these cationic clusters is indicated by considerable HOMO-LUMO gaps and positive dissociation energies.More intriguingly,these alkaline-earth-metal-based cations have advantages over alkali-metal-based superalkalis in two aspects:1)they possess much larger binding energy values;2)they can keep the chemical stability along with the increasing cluster size.Therefore,it is proposed here that the alkaline-earth-metal atoms could partner with halogens to construct stable cations of low EA value,which may add new candidates to the superalkali family.4.The equilibrium structures,stability and magnetic properties of the Sc?BO₂?_n^-/0?n=1-4?clusters were investigated on the basis of density functional theory calculations.The BO₂ ligands prefer to stretch out in the most stable Sc?BO₂?_n^-anions but tend to get together in the lowest-lying Sc?BO₂?₄ structure.According to the MP2results,the Sc?BO₂?₄^-species could be classified as hyperhalogen anions since they have larger vertical electron detachment energies?VDEs,5.44-8.85 eV?than that of superhalogen anion BO₂^-.With titanium and vanadium playing the role of central atom,the Ti?BO₂?_n^-/0?n=1-5?and V?BO₂?_n^-/0?n=1-6?clusters were studied in the same vein.In these cases,the central transition metal atoms are inclined to keep their intrinsic spin.In addition,the hyperhalogen identity of the Ti?BO₂?_n^-?n=4,5?and V?BO₂?_n^-?n=3-6?species were also confirmed by the calculated VDE values.