Theoretical Design Of Quasi-halogen Superatom With Considerable Magnetism

In recent years,atomic clusters with various properties have been applied in the fields of magnetics,electricity,optics,etc.,which makes the design and study on the properties of atomic clusters become a popular topic.Among all the metal clusters,aluminum clusters have been widely studied because of their special physico-chemical properties.The quasi-halogen superatom Al₁₃ is the most typical example,which longs for one extra electron to fill the unoccupied 2P molecular orbital and achieve an electron closed shell.Based on Al₁₃,scientists have reported and characterized a variety of doped aluminum clusters.However,hitherto there are few researches on the lanthanide doped aluminum clusters.In this thesis,the lanthanide element doped aluminum clusters,namely Al₁₂Gd and Al12Gd^—,have been theoretically studied by the aid of quantum chemistry methods.Results show that the global minimum of Al₁₂Gd is of nonet state,and has an icosahedral geometry,in which the impurity atom Gd is located at the bottom of the Al₁₂ framework.The global minimum of Al12Gd^—is of octet state,and its geometric skeleton is similar to that of Al₁₂Gd.According to molecular orbital analysis,the 4f electrons of Gd atom tend to be localized in the atomic orbital.And the additional electron obtained by Al₁₂Gd tends to fill the 1F molecule orbital,thus resulting in the stable cluster Al12Gd^—.This shows the origin of the halogen-like properties and magnetic characteristics of Al₁₂Gd.Furthermore,the quasi-halogen properties of Al₁₂Gd is also reflected when it comes to its behavior when interacting with other species:(1)Al₁₂Gd tends to accept an electron when forming complexes with(super)alkali atoms,just as halogen atoms do;(2)an alkaline-earth atom can combine with two Al₁₂Gd units to mimic Ca Cl₂ and Ca Br₂ molecules;(3)two Al₁₂Gd clusters can also form a Cl₂-like dimer(Al₁₂Gd)₂.According to the NBO analysis,the Al₁₂Gd cluster maintains its original magnetic moment,and the 4f electrons of Gd atom contribute the magnetic moments in these compounds.In order to reveal the adsorption behavior of magnetic superatom Al₁₂Gd on the surface of graphene,we have also investigated the structural stability,electronic properties and magnetism of the adsorption system.Results show that the Al₁₂Gd cluster maintains its original configuration after adsorbed on the surface of graphene.There is a weak charge-transfer interaction between the Al₁₂Gd cluster and graphene.In the adsorption system,the Al₁₂Gd cluster loses electrons,while the substrate gains electrons.These results might further stimulate the study of doped aluminum clusters.Besides,the characteristic of f electrons and the non-Aufbau electronic structure mentioned in this work provide a fresh idea for the design of new magnetic superatoms.