The universal parameter nonorthogonal tight binding scheme proposed by Menon and Subbaswamy was used to optimize the geometrical structures, binding energies and electron affinities of small germanium clusters Ge ...The universal parameter nonorthogonal tight binding scheme proposed by Menon and Subbaswamy was used to optimize the geometrical structures, binding energies and electron affinities of small germanium clusters Ge n ( n =2—20). A complete agreement with available ab initio results from the lowest energy structures for Ge 2—Ge 6 was obtained and reasonable structures for these clusters were predicted and compared with those of corresponding silicon clusters in the range of n =7—20 . The averaged discrepancy with experiments in binding energies for n =2—7 is about 6% and the calculated electron affinities agree well with the measured values in the range of n =2—8 as well.展开更多
The relation between the stability of icosahedral clusters and the range of interaction potential is discussed.We found that the stability of icosahedral clusters nay decrease with decreasing range of interaction pote...The relation between the stability of icosahedral clusters and the range of interaction potential is discussed.We found that the stability of icosahedral clusters nay decrease with decreasing range of interaction potential.A simple formula about the critical number of icosahedral clusters and the range of interaction potential(M^(1/3)_(c)=A_(1)+A_(2)r^(2)_(eff))was proposed.The calculation of the stability of icosahedral fullerence molecular clusters shows that our idea is right.展开更多
Molecular dynamics simulation has been carried out for melt Al under the constant-temperature and constant-pressure. The interaction between atoms is described by tight-binding many body potentials based on the second...Molecular dynamics simulation has been carried out for melt Al under the constant-temperature and constant-pressure. The interaction between atoms is described by tight-binding many body potentials based on the second-moment approximation to the electronic density of states. The pair correlation function and the pair analysis technique are used to reveal the structural features of liquid Al under the normal and high pressure. The high pressure is favorable to the existence of bcc-cluster 1661 and 1441, but has no effect on the fcc-cluster 1421. The bond pair 1551 and 1541 with fivefold symmetry exists at high pressure. The microstructure of liquid is more similar to the structure of non-crystalline than to crystalline. The simulation results are supported by the x-ray experimental results.展开更多
The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,...The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,and simultaneously an s-p gap minimum,but not necessarily an ionization potential maximum,where HOMO-LUMO gap denotes the energy gap between the highest occupied orbital and the lowest unoccupied orbital of the cluster.Also revealed is an irregular odd-even alternation in HOMO-LUMO gaps for Al_(n)(n=7-24).Cluster geometry either contributes to or dominates these findings.展开更多
文摘The universal parameter nonorthogonal tight binding scheme proposed by Menon and Subbaswamy was used to optimize the geometrical structures, binding energies and electron affinities of small germanium clusters Ge n ( n =2—20). A complete agreement with available ab initio results from the lowest energy structures for Ge 2—Ge 6 was obtained and reasonable structures for these clusters were predicted and compared with those of corresponding silicon clusters in the range of n =7—20 . The averaged discrepancy with experiments in binding energies for n =2—7 is about 6% and the calculated electron affinities agree well with the measured values in the range of n =2—8 as well.
基金The project supported by National Natural Science Foundation of Chinathe Natural Science Foundation of Shandong Province of China under Grant No.Q99A04
文摘The relation between the stability of icosahedral clusters and the range of interaction potential is discussed.We found that the stability of icosahedral clusters nay decrease with decreasing range of interaction potential.A simple formula about the critical number of icosahedral clusters and the range of interaction potential(M^(1/3)_(c)=A_(1)+A_(2)r^(2)_(eff))was proposed.The calculation of the stability of icosahedral fullerence molecular clusters shows that our idea is right.
基金Supported by the National Natural Science Foundation of China under Grant No.29890210the Shandong Natural Science Foundation of China under Grant No.Z99F01.
文摘Molecular dynamics simulation has been carried out for melt Al under the constant-temperature and constant-pressure. The interaction between atoms is described by tight-binding many body potentials based on the second-moment approximation to the electronic density of states. The pair correlation function and the pair analysis technique are used to reveal the structural features of liquid Al under the normal and high pressure. The high pressure is favorable to the existence of bcc-cluster 1661 and 1441, but has no effect on the fcc-cluster 1421. The bond pair 1551 and 1541 with fivefold symmetry exists at high pressure. The microstructure of liquid is more similar to the structure of non-crystalline than to crystalline. The simulation results are supported by the x-ray experimental results.
基金Supported by the National Natural Science Foundation of China under Grants Nos.19574059 and 19634030.
文摘The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,and simultaneously an s-p gap minimum,but not necessarily an ionization potential maximum,where HOMO-LUMO gap denotes the energy gap between the highest occupied orbital and the lowest unoccupied orbital of the cluster.Also revealed is an irregular odd-even alternation in HOMO-LUMO gaps for Al_(n)(n=7-24).Cluster geometry either contributes to or dominates these findings.
