Xin Liu

Publications (3)7.96 Total impact

• Article: Effects of Structure, Temperature, and Strain Rate on Mechanical Properties of SiGe Nanotubes

  Xin Liu, Dapeng Cao, Aiping Yu
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  ABSTRACT: The effects of structure, temperature, and strain rate on mechanical properties of all the SiGe nanotubes in armchair and zigzag structures (n = 4−13) in two atomic arrangement types are investigated by classical molecular dynamics simulation. During the extending tests, we observe three structural transformations from initial structure, tensile structure, to critical structure deformation. The simulation results indicate that the Young’s modulus of nanotubes is closely dependent on their diameter, chirality, and arrangement structure. The type 1 (alternating atom arrangement type) armchair SiGe nanotube exhibits the largest Young’s modulus, compared with other nanotubes with the same index n. By exploring the effects of temperature and strain rate on mechanical properties of SiGe nanotubes, it is found that the higher temperature and lower strain rate lead to the lower critical strain and tensile strength. Furthermore, it is also found that the critical strains for both armchair and zigzag nanotubes in two arrangement types are significantly dependent on the tube diameter and chirality. The armchair type 1 nanotube exhibits the highest mechanical critical strain and tensile strength among all these nanotubes with the same index n. On the basis of the transition-state theory model, we predict that the critical strain of the SiGe (6,6) type 1 nanotube at 300 K, stretched with a strain rate of 5%/h, is about 3.38%, which is in good agreement with the recent experimental results. Our results might provide potential applications in manipulating mechanical and electromechanical properties of the nanostructures suitable for electronic devices.
  02/2010;
• Article: The structure, energetics and thermal evolution of SiGe nanotubes.

  Xin Liu, Daojian Cheng, Dapeng Cao
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  ABSTRACT: The structure, energetics and thermal behavior of all the SiGe nanotubes in armchair and zigzag structures (n = 4-10) and two atomic arrangement types are investigated using the ab initio method and classical molecular dynamics simulations. Gearlike and puckering configurations of SiGe nanotubes are obtained. The simulation results indicate that large-diameter nanotubes are more stable than small-diameter ones. Moreover, the type 1 (alternating atom arrangement type) zigzag nanotubes are always more energetically favorable than the type 2 (layered atom arrangement type) zigzag nanotubes. During the melting process, the melting-like structural transformations from the initial nanotube to the compact nanowire take place first, and then the compact nanowires are changed into agglomerate structures at higher temperature. It is also found that the melting-like temperatures of Ge-substituted silicon nanotubes decrease with increase of the Ge concentration.
  Nanotechnology 09/2009; 20(31):315705. · 3.98 Impact Factor
• Article: Surface segregation of Ag–Cu–Au trimetallic clusters

  Daojian Cheng, Xin Liu, Dapeng Cao, Wenchuan Wang, Shiping Huang
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  ABSTRACT: Segregation phenomena of Ag–Cu–Au trimetallic clusters with icosahedral structure are investigated by using a Monte Carlo method based on the second-moment approximation of the tight-binding (TB-SMA) potentials. We predict that the Ag atoms segregate to the surface of the Ag–Cu–Au trimetallic icosahedral clusters. The Ag concentrations in the surface layer of the clusters are about 11–29 at.% higher than the overall Ag concentration in all the cases studied. The simulation results also indicate that the Au atoms are mainly distributed in the middle shell and the Cu atoms are located in the center for the 147-, 309-, 561- and 923-atom clusters at 300 K. The segregation phenomena of the Ag, Au and Cu atoms in the Ag–Cu–Au trimetallic clusters are mainly due to the different surface energies of the Ag, Au and Cu atoms. It is found that the size and composition have little effect on the segregation phenomena of Ag, Au and Cu atoms in the Ag–Cu–Au trimetallic cluster.
  Nanotechnology 10/2007; 18(47):475702. · 3.98 Impact Factor