| Amsterdam Density Functional (ADF) software package is internationally acknowledged as an efficient calculation program. It is based on the analysis of the first principles density functional theory, applying linear scaling and parallel implementations technology, since it is quite suitable for cluster computing research. In this paper, MAln (M=Cr, Mn, Fe, Co, Ni; n=2-12) clusters and Cn-nNn (n=4-11) non-metallic clusters have been investigated systematically by using the ADF program.Firstly, we have studied the influence of3d transition metal impurities on the ground-state structures, stability and magnetism of MAln clusters in detail. Some new results have been obtained as follows:1. The impurity atoms (Cr, Mn, Fe, Co, Ni) not only cause various distortions in the mixed structures but also change the energy order of the isomers. It is reported that the stable structures for Aln+i (n<5) clusters are planar. However, for the mixed clusters, except for MAl2, all the other doped clusters adopt three-dimensional structures.2. The results reveal that the stability of Al7cluster is better than the other pure aluminum clusters, interestingly, the mixed clusters as CrAl6, MnAl6, CoAl7and NiAly containing6or7Al atoms also exhibit the high stability. Furthermore, individual cluster like FeAl4displays remarkable stability due to their closed electronic shells.3.3d transition metal impurity atoms would change the magnetism of the host aluminum clusters. Except for the CrAl5cluster associating with1μm normal magnetic moment, the other CrAln and MnAln (n=2-12) clusters show extraordinary magnetism with a net magnetic moment of2μB-5μB. Besides, half the number of the CrAln and MnAl,,(n=2-12) clusters possess a net magnetic moment of2μB-4μB.There are no anomalous magnetic moments exhibited in the other clusters. The analysis indicates the magnetic moments of these clusters are from the strong sp-d hybridization and3d impurities.Secondly, we have calculated the binding energies for the anions, neutrals and cations of CuAln and ZnAln (n=2-12) clusters, in order to research the effect of non-magnetic impurity atoms on the structures and magnetism of original pure aluminum clusters. The conclusions can be as follows:1. It indicates that most of the lowest energy structures for the CuAln and ZnAln (n=2-12) clusters can be obtained by substituting one aluminum atom with3d metal atom. But the impurities have caused structural distortion, and resulted in the symmetry decrease. Nonetheless, as an exception, CuAl12adopts icosahedral symmetry (Ih) and the symmetry is higher than the that of Al13.2. CuAl3and ZnAl2have the same magnetic moments of2μB, and both CuAl12and ZnAl3have the magnetic moments of3μB-This shows that the non-magnetic clusters probably present magnetism, after they are doped with non-magnetic impurities.At last, we have studied the electronic structures, bonding characters and stabilities of the CmNn (m, n=1-10,4≤m+n≤11) clusters in detail. It is found that all the species of Nn (n=4-11) clusters are linear zigzag structures. However, the zigzag points are straightened after substituting carbon for nitrogen atoms. It is because that adjacent nitrogen atoms form a π bond and two a bonds, and carbon atoms prefer to form π bonds with neighbor atoms. In addition, the stabilities mainly depend on the number of nitrogen atoms in the CmNn (m, n=1-10,4≤m+n≤11) clusters. No matter what proportion of the mixed clusters, they would possess relatively higher stability if they are the odd-numbered clusters containing4nitrogen atoms or the even-numbered clusters including2nitrogen atoms. |
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