The metallic softness parameterαr 0 determines the structure of the cluster and governs the rule of magic numbers. Using molecular dynamic method, the stable structures and magic numbers are determined for the cluste...The metallic softness parameterαr 0 determines the structure of the cluster and governs the rule of magic numbers. Using molecular dynamic method, the stable structures and magic numbers are determined for the clusters consisting of 13 up to 147 atoms in medium range Morse potentials, which is suitable for most of metals. As the number of atoms constituting the cluster increases, the stable structures undergo transition from face-centered (FC) to edge-centered (EC) structures. The magic number take ones of FC series before transition and take ones of EC series after that. The transition point from FC to EC structures depends on the value of softness parameter.展开更多
The stable structures and energies of Ni clusters were investigated using particle swarm optimization(PSO)combined with simulated annealing(SA).Sutton-Chen many-body potential was used in describing the interatomic in...The stable structures and energies of Ni clusters were investigated using particle swarm optimization(PSO)combined with simulated annealing(SA).Sutton-Chen many-body potential was used in describing the interatomic interactions.The simulation results indicate that the structures of Ni clusters are icosahedral-like and binding energy per atom tends to approach that of bulk materials when the atoms number increases.The stability of Ni clusters depends not only on size but also on symmetrical characterization.The structure stability of Nin clusters increases with the increase of total atom number n.It is also found that there exists direct correlation between stability and geometrical structures of the clusters,and relatively higher symmetry clusters are more stable.From the results of the second difference in the binding energy,the clusters at n=3 is more stable than others,and the magic numbers effect is also found.展开更多
In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic...In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of those found in corresponding bulk materials. Silicon agglomerates found in Silicon Rich Oxide (SRO) films have optical properties, which have reported as depended directly on nano-crystal size. Furthermore, the room temperature photoluminescence (PL) of Silicon Rich Oxides (SRO) has repeatedly generated a huge interest due to their possible applications in optoelectronic devices. However, a plausible emission mechanism has not yet widespread acceptance of the scientific community. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6 - 31G* to calculate the optical and electronic properties of small (six to ten silicon atoms) and medium size clusters of silicon (constituted of eleven to fourteen silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism experimentally found in thin SRO films.展开更多
A molecular dynamics simulation study has been performed for a large systemconsisting of 100000 liquid metal Al atoms to investigate the formation and magic numbercharacteristics of the cluster configurations formed d...A molecular dynamics simulation study has been performed for a large systemconsisting of 100000 liquid metal Al atoms to investigate the formation and magic numbercharacteristics of the cluster configurations formed during the rapid solidification processes. Thecluster-type index method (CTIM) has been adopted to describe various types of clusterconfigurations. The results indicate that the icosahedral clusters (12 0 12 0) and theircombinations play the most important role in the rnicrostructure transitions during solidificationprocesses; for the cluster configurations of different levels formed by various combinations withdiffering numbers of basic clusters, their size distributions possess obvious magic number sequencewhich is in turn as 13(13), 19(21), 26-28(27), 32-33(32), 39-40, 43-44, 48..., (those in bracket arethe corresponding value in liquid state); the magic numbers correspond to the peak value positionsof the cluster numbers for corresponding level formed with various combinations by 1, 2, 3, 4, 5, 6,7, ...basic clusters, respectively. This magic number sequence is in good agreement with theexperimental results obtained by Harris et al. At the same time, this simulation study also gives ascientific and reasonable explanation to these experimental results.展开更多
The production mechanism of Cu/Cl binary clusters were investigated by laser vaporization of CuCl, CuCl2, CuCl2·2H2O by time-of-flight mass spectrometry. We found that lager cluster size can be detected by using ...The production mechanism of Cu/Cl binary clusters were investigated by laser vaporization of CuCl, CuCl2, CuCl2·2H2O by time-of-flight mass spectrometry. We found that lager cluster size can be detected by using CuCl2·2H2O solid pellets than CuCl2 and CuCl. Only Cu+(CuCl)n, (CuCl)n, n <8 were observed when 532 um laser vaporized the CuCl. We also found almost the same cluster using CuCl2 and CuCl2·2H2O in the same mass range, deficit Cu clusters were dominated for clusters with more than five Cu atoms when using CuCl2, CuCl2·2H2O compounds. The relation of relative intensity In2:/In-1In+1 vs. different size of clusters were almost the same using different compounds above. (CuCl)3+.(CuCl)+6 ions in (CuCl)+n series, and Cu6Cl+5 in Cu(CuCl)+n series have special stability. The magic number observed above are different from those of alkali halide (MX) clusters, hexagonal structures were proposed for the above magic number clusters.展开更多
Magic number cluster ion Mn5+ and abundant Mn/O cluster ions havc been formed by 532nm laser ablation of MnCO3 solid sample with time-of-flight mass spectroscopy detection. The experimental results show that Mn5+ was ...Magic number cluster ion Mn5+ and abundant Mn/O cluster ions havc been formed by 532nm laser ablation of MnCO3 solid sample with time-of-flight mass spectroscopy detection. The experimental results show that Mn5+ was formed in the cooler dilute tail region of the plume produced by laser ablation, while Mn/O cluster ions were mainly formed in the hotter dense preceding portion of the plume, they all were produced by postablation cluster growth in the ablation plume. Pentagonal with D(5h) symmetry is the possible structure of Mn5+, which is supported by our ab initio calculation.展开更多
基金Supported by the National Natural Science Foundation of China(196 740 42 198340 70 ) Science and Technology Program of Natio
文摘The metallic softness parameterαr 0 determines the structure of the cluster and governs the rule of magic numbers. Using molecular dynamic method, the stable structures and magic numbers are determined for the clusters consisting of 13 up to 147 atoms in medium range Morse potentials, which is suitable for most of metals. As the number of atoms constituting the cluster increases, the stable structures undergo transition from face-centered (FC) to edge-centered (EC) structures. The magic number take ones of FC series before transition and take ones of EC series after that. The transition point from FC to EC structures depends on the value of softness parameter.
基金Project(60371046)supported by the National Natural Science Foundation of China
文摘The stable structures and energies of Ni clusters were investigated using particle swarm optimization(PSO)combined with simulated annealing(SA).Sutton-Chen many-body potential was used in describing the interatomic interactions.The simulation results indicate that the structures of Ni clusters are icosahedral-like and binding energy per atom tends to approach that of bulk materials when the atoms number increases.The stability of Ni clusters depends not only on size but also on symmetrical characterization.The structure stability of Nin clusters increases with the increase of total atom number n.It is also found that there exists direct correlation between stability and geometrical structures of the clusters,and relatively higher symmetry clusters are more stable.From the results of the second difference in the binding energy,the clusters at n=3 is more stable than others,and the magic numbers effect is also found.
文摘In systems in atomic and nano scales such as clusters or agglomerates constituted of particles from a few to less than one hundred of atoms, quantum confinement effects are very important. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of those found in corresponding bulk materials. Silicon agglomerates found in Silicon Rich Oxide (SRO) films have optical properties, which have reported as depended directly on nano-crystal size. Furthermore, the room temperature photoluminescence (PL) of Silicon Rich Oxides (SRO) has repeatedly generated a huge interest due to their possible applications in optoelectronic devices. However, a plausible emission mechanism has not yet widespread acceptance of the scientific community. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6 - 31G* to calculate the optical and electronic properties of small (six to ten silicon atoms) and medium size clusters of silicon (constituted of eleven to fourteen silicon atoms). With the theoretical calculation of the structural and optical properties of silicon clusters, it is possible to evaluate the contribution of silicon agglomerates in the luminescent emission mechanism experimentally found in thin SRO films.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 50271026).
文摘A molecular dynamics simulation study has been performed for a large systemconsisting of 100000 liquid metal Al atoms to investigate the formation and magic numbercharacteristics of the cluster configurations formed during the rapid solidification processes. Thecluster-type index method (CTIM) has been adopted to describe various types of clusterconfigurations. The results indicate that the icosahedral clusters (12 0 12 0) and theircombinations play the most important role in the rnicrostructure transitions during solidificationprocesses; for the cluster configurations of different levels formed by various combinations withdiffering numbers of basic clusters, their size distributions possess obvious magic number sequencewhich is in turn as 13(13), 19(21), 26-28(27), 32-33(32), 39-40, 43-44, 48..., (those in bracket arethe corresponding value in liquid state); the magic numbers correspond to the peak value positionsof the cluster numbers for corresponding level formed with various combinations by 1, 2, 3, 4, 5, 6,7, ...basic clusters, respectively. This magic number sequence is in good agreement with theexperimental results obtained by Harris et al. At the same time, this simulation study also gives ascientific and reasonable explanation to these experimental results.
文摘The production mechanism of Cu/Cl binary clusters were investigated by laser vaporization of CuCl, CuCl2, CuCl2·2H2O by time-of-flight mass spectrometry. We found that lager cluster size can be detected by using CuCl2·2H2O solid pellets than CuCl2 and CuCl. Only Cu+(CuCl)n, (CuCl)n, n <8 were observed when 532 um laser vaporized the CuCl. We also found almost the same cluster using CuCl2 and CuCl2·2H2O in the same mass range, deficit Cu clusters were dominated for clusters with more than five Cu atoms when using CuCl2, CuCl2·2H2O compounds. The relation of relative intensity In2:/In-1In+1 vs. different size of clusters were almost the same using different compounds above. (CuCl)3+.(CuCl)+6 ions in (CuCl)+n series, and Cu6Cl+5 in Cu(CuCl)+n series have special stability. The magic number observed above are different from those of alkali halide (MX) clusters, hexagonal structures were proposed for the above magic number clusters.
文摘Magic number cluster ion Mn5+ and abundant Mn/O cluster ions havc been formed by 532nm laser ablation of MnCO3 solid sample with time-of-flight mass spectroscopy detection. The experimental results show that Mn5+ was formed in the cooler dilute tail region of the plume produced by laser ablation, while Mn/O cluster ions were mainly formed in the hotter dense preceding portion of the plume, they all were produced by postablation cluster growth in the ablation plume. Pentagonal with D(5h) symmetry is the possible structure of Mn5+, which is supported by our ab initio calculation.
