The geometrical structure, frequency and electronic properties of the NiMgn(n=1—12) clusters have been studied with the generalized gradient approximation (GGA) based on the density functional theory (DFT) with the consideration of spin multiplicity. The results indicate that: when n is 1 or 2, the spin multiplicity of the ground state structures of the clusters is triplet while it is singlet from n≥3. The ground state structures of the host clusters are changed obviously due to the encapsulation of Ni atom for n≤8, the growth patterns of the ground state structures of the NiMgn clusters are dominated by the trigonal bipyramidal, as well as the octahedron structures. The evolution behaviors of the ground state structures based on the trigonal prism of the host clusters are partly modified from n≥9. The Ni atom completely falls into the center of the host clusters as n≥6. The doping of Ni atoms increases the average binding energy, but reduces the energy gap of the host clusters. n=4, 6 and 10 are the magic numbers. The 3d and 4p orbitals of the Ni atom for different sized clusters play distinct roles in the s-p-d orbital hybridization. The NiMg6 cluster with higher symmetry Oh not only possesses improved stability, but also has the smallest energy gap (just about 0.25eV) of all of the NiMgn clusters.
The geometry structures, stabilities and chemical bonding properties of the YnNO(n=1–12) clusters are studied in the generalized gradient approximation based on the density functional theory with the consideration of spin multiplicities. The results show that NO adsorption changes the basic frameworks of the corresponding Yn clusters with n=5, 7, 8, 10. The obvious elongation of N–O bond length and the attenuate vibrational frequency indicate that the adsorption of NO on Yn cluster can be regarded as the dissociative adsorption. The chemical bondings of N–Y and O–Y both simultaneously play an important role in enlarging the adsorption energy of YnNO clusters. Specially, Y3NO, Y5NO, and Y8NO have the giant adsorption energies (9.92, 9.24, and 9.82 eV) coupled with the break of the N–O bond. The calculated second-order energy differences suggest that the NO adsorption has influences on the stabilities and bonding properties of Yn clusters. The appearance of the couple electrons, arising from the sp3 hybridization of N and O atom, not only leads to the fracture of N–O bond, but also enhances the ability to form N–Y bond and O–Y bond, which has important effects on the high stabilities of Y3NO, Y5NO, and Y8NO clusters.
The geometries, total energies, and frequencies of ZrnCo (n=1—13) clusters have been systematically investigated by using density functional theory with the generalized gradient approximation. The equilibrium geometries, stabilities, gap and magnetism have been determined. The results show that the relative stabilities of Zr4Co, Zr7Co, Zr9Co and Zr12Co are stronger than other sized clusters, indicating that they are magic number clusters, and especially, the true ground state for Zr12Co cluster has icosahedral structure with Ih symmetry. Moreover, the stability of Zr12Co is the strongest of all the investigated clusters. The magnetic moment of ZrnCo clusters mainly comes from the localized d electron. The system magnetic moment may be divided into three stages along with the size change: n=1—3 corresponds to the stable magnetic moment, the magnetic moment of ZrnCo clusters starts to show vibration quenching from n=4, until n=8 when the magnetic moments is completely quenched. The charge transfer and the strong hybridization between s, p and d states might be one major reason for quenching of the magnetic moment of ZrnCo clusters. Meanwhile, the clusters which are composed of transition metals doped in different characteristic materials is worth further studying, for example, TMX12 and Zr13TM clusters have interestingly similar structures, stability and magnetism.
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