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Magic Number (magic + number)

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Chemistry100%

Selected Abstracts

Structures and stability of lithium monosilicide clusters SiLin (n = 4,16): What is the maximum number, magic number, and core number for lithium coordination to silicon?

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2008
Ning He
Abstract In the coordination, hypervalent and cluster chemistry, three important characteristic properties are the maximum coordination number, magic number, and core coordination number. Yet, few studies have considered these three numbers at the same time for an MLn cluster with n larger than 8. In this article, we systematically studied the three properties of SiLin (n = 4,16) clusters at the B3LYP/6-31G(d), B3LYP/6-311++G(2d), and CCSD(T)/6-311++G(3df)//B3LYP/6-311++G(2d) (for energy only) levels. Various isomeric forms with different symmetries were calculated. For each SiLin (n = 4,9), silicon cohesive energy (cE) from SiLin , Si + Lin reaction, vertical ionization potential (vIP), and vertical electron affinity (vEA) were obtained for the lowest-energy isomer. We found that the maximum Li-coordination number of Si is 9, which is the largest number among the known MLin clusters. All cE, vIP, and vEA values predicted that 6 is the magic Li-coordination number of Si. For small SiLin (n , 6) clusters, Li atoms favor direct coordination to Si, whereas for larger SiLin (n , 7) clusters, there is a core cluster that is surrounded by excessive Li atoms. The core Li-coordination number is 6 for SiLin (n = 7,8), 7 for SiLin (n = 9,10), 8 for SiLin (n = 11,15) and 9 for SiLin (n , 16). Through the calculations, we verified the relationship between the structure and stability of SiLin with the maximum coordination number, magic number, and core coordination number. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]

Formation of binary alloy cluster ions from group-14 elements and cobalt and comparison with solid-state alloys

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2001
Xia Zhang
By using laser ablation on mixtures of transition metal cobalt and group-14 elements, binary alloy cluster anions were produced while no binary alloy cluster cations were detected, and the homocluster cations of group-14 elements appeared at very low abundance. The differences between clustering abilities of germanium, tin and lead with cobalt are described, and the chemical bonds in the binary alloy cluster anions appear to indicate a transition from covalent to metal bonds. The cluster anion [CoPb10], appears in very high abundance (magic number), and an endohedral structure is proposed for this cluster. The cluster anion [CoPb12],, also representing a magic number, probably has an icosahedral structure. Compared with solid-state Co/Ge binary alloys, the compositions of most binary alloy cluster anions are germanium-rich, in which the covalent bonds are predominant. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Supershells in deformed harmonic oscillators and atomic clusters

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2002
Dennis Bonatsos
Abstract From the mathematical point of view, the appearance of supershells is a general feature of potentials having relatively sharp edges. In physics, supershells have been observed in systems of metal clusters, which are also known to exhibit an underlying shell structure with magic numbers intermediate between the magic numbers of the 3-D isotropic harmonic oscillator and those of the 3-D square well. In the present study, Nilsson's modified harmonic oscillator (without any spin,orbit interaction), as well as the 3-D q -deformed harmonic oscillator with uq(3) , soq(3) symmetry, are considered. The former model has been used for an early schematic description of shell structure in metal clusters, while the latter has been found to successfully reproduce the magic numbers of metal clusters up to 1500 atoms, the expected limit of validity for theories based on the filling of electronic shells. The systematics of the appearance of supershells in the two models will be considered, putting emphasis on the differences between the spectra of the two oscillators. While the validity of Nilsson's modified harmonic oscillator framework is limited to relatively low particle numbers, the 3-D q -deformed harmonic oscillator gives reliable descriptions of the first supershell in metal clusters, which lies within its region of validity. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source]