First-principles Study Of Hydrogenated Silicon Carbon Si_nC_nH_2n（n=9-11）Clusters And Their Endohedral Doping With Atoms

One of the important issues of cluster investigation is to obtain the most stable clusters with certain composition. Hydrogenated clusters is one of the methods to obtain stable clusters and has been investigated totally. In this thesis, using the first principles method based on the density functional theory, we studied the structures and stabilities of SinCnH2n(n=9-11) clusters. Endohedral doping of the empty SinCnH2n(n=9-11) cages with different guest atoms on structures, stabilities, electronic and magnetic properties has been systematically investigated.Compared with SinCn(n=9-11) clusters, the arrangement of silicon atoms, in SinCnH2n(n=9-11) clusters is more regular, while the arrangement of carbon atoms is amost no change. The average bond length between silicon atoms becomes shorter after the SinCn(n=9-l 1) clusters are hydrogenated. In SinCnH2n(n=9-11) clusters, the average binding energies of silicon and carbon atoms are larger than that of corresponding SinCn(n=9-11) clusters. In order to further check the stability of the most lowest-energy structures of SinCnH2n(n=9-11) clusters, we displaced a silicon atom or a carbon atom or a hydrogen atom considerably far from its equilibrium position randomly. However, after reoptimization, the cage returns to its equilibrium structure, showing that the lowest-lying structures of SinCnH2n(n=9-11) clusters are quite stable.Most of the endohedral doped atoms can not stay inside the cage-like structure of SinCnH2n(n=9-11) clusters. They floated toward silicon atoms and bonded with silicon atoms. It is found that the endohedral doping with atoms affects the HOMO-LUMO gap of the clusters significantly and therefore the optical property of the SinCnH2n(n=9-11) clusters may be modified by doping in order to design materials with desired properties. The electronic charge of all the doping atoms is negative, which means that the charge transfers from the empty cage to the guest atoms. For the transitional atom-doped SinCnH2n(n=9-11) clusters, the total magnetic moments are larger than that of transitional atom-doped SinCn(n=9-11) clusters, which can reach 3μB. The total magnetic moments for the most atom-doped clusters are mainly contributed by doping atoms.