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Molecular dynamics simulation was used to investigate the mechanical properties of (5, 5), and (10, 10) single-walled nanocoils, as well as (5, 5)@(10, 10) double-walled carbon nanocoils (CNCS). The second reactive empirical bond order potential was employed to model the interaction between carbon atoms. The atomic slip vector and sequential slip vector were used to investigate the structural variations at different strains during the tension process. The yield stress, maximum tensile strength, and Young’s modulus were determined from the tensile stress–strain profiles. The results show that the nanocoils have superelastic characteristics and have a high strength similar to that of carbon nanotube with same chirality.

The mechanical properties of Ni-Ta crystallizationand binary bulk metallic glasses (BMG) were investigated for this study at the nanoscale. First, the Ta9Ni3 crystals are formed by space group, and structures with different ratios (Ta1Ni1, BTa8Ni4, BTa9Ni3, BTa7Ni5) were put into unit cell randomly. The optimizations of BMG structures are performed by Density functional theory (DFT) calculation to find the stable amorphous structures and corresponding energy. The FMM is utilized to obtain the suitable parameters of tight-binding potential bystable amorphous structures and corresponding energies. Finally, we employ molecular dynamics (MD) simulation to study mechanical properties of Ni/Ta crystallization and BMG, such as atomistic stress-strain, plastic and elastic deformation, and elastic modulus.

In our previous study, we have proven two ultrathin Pd nanowires can prevent from Pd embrittlement. In this study, we further demonstrate the material properties of a larger Pd nanowire. Both classical potential function and density functional theory calculation were used. The results show once the larger Pd nanowire has interior Pd atoms, hydrogen atoms can stably stay within the nanowire. Consequently, the hydrogen embrittlement could happen with a higher probability than two ultrathin Pd nanowires reported in our previous study.

The collective dynamic behavior of carbon atoms of a (17, 0) zigzag single wall carbon nanotube is investigated under tensile strains by molecular dynamics (MD) simulations. The “slip vector” parameter is used to study the collective motion of a group of atoms and the deformation behavior in three different directions (axial, radial, and tangential) of a (17, 0) carbon nanotube. The variations of radial slip vectors indicate almost all carbon atoms of the (17, 0) carbon nanotube will stay on the cylindrical surface before the yielding of the single wall carbon nanotube (SWNT). Furthermore, the tangential vectors show kinking deformation for the (17, 0) zigzag tube only rarely appears when the crack occurs. Non-symmetrical deformation around a carbon atom along the axial direction also can be found. The variations in the slip vector values of each atom display a symmetrical crack along the horizontal direction and normal to the tube axis. Chain-like structures with 3–4 atoms can be observed, with the number of chain-like structures decreasing before the breakage of the SWNT. The mechanical properties and dynamic behavior of a (17, 0) zigzag SWNT under tensile strain are also compared with that of a (10, 10) armchair tube in our previous study (Weng et al. 2009).

Thermodynamic properties of titanium dioxide (TiO 2 ) n ( n = 1–6) nanoparticles were studied by first-principle molecular dynamics (MD) simulation. The configurations for (TiO 2 ) n ( n = 1–6) nanoparticles with global minimum energies can be initially obtained by MD simulation combined with the fast inertial relaxation engine algorithm. These structures can be further refined by density functional theory simulation. The variation of internal energies and Lindemann criteria with the simulation temperature was used to indicate the occurring of phase change for (TiO 2 ) n ( n = 1–6) nanoparticles. The effect of size and geometry on the thermodynamic properties of TiO 2 nanoparticles was also found.

Molecular dynamics simulation is used to investigate the dynamic properties of water molecules inside an Au nanotube in different water densities. From the oxygen density profiles, some characteristic peaks appear at specific regions. In order to observe the dynamical behaviors of water molecules in different portions in the Au nanotube, these specific peaks are divided into three regions—I, II, and III—which are 0−4, 4−7, and 7−10 A, respectively, as measured from the center of the tube to the inside wall of the tube. Since the strength of hydrogen bonds between water molecules within regions I and II can overcome the interaction between the Au nanotube and the water molecules within those regions, the major peaks of the region I and II spectra are similar to those of bulk water. However, the strength of hydrogen bonds between water molecules within region III cannot overcome the interaction between the Au nanotube and the water molecules within that region, so the major peak of the region III spectrum s...

Understanding the mechanical properties of multilayered metal thin films is very important for their applications in nanoscale devices. Nanoindentation is one of the widely used tools for examining the mechanical properties of metal thin films. In the present study, molecular dynamics simulation was employed to investigate the nanoindentation behavior of a Cu(100)/Cu(110) bilayered thin film. The load-displacement response and the detailed deformation structure of the copper thin film during the nanoindentation were inspected and compared with those of Cu(100) and Cu(110) thin films. It was found that at the indenting stage the maximum indentation load of the bi-layered thin film is lower than that of its ingredients, however, they have nearly the same maximum indentation load. At the retracting stage, the maximum attractive force of the bilayered thin film was found near that of its ingredients but occurred much earlier than the ingredients. The detailed deformation structure of the bilayered thin film was observed to be similar to that of the ingredients and correlated very well with the load-displacement response.

Molecular dynamics simulation was carried out to investigate the behavior of (5,5) and (10,10) armchair carbon nanotubes in water under tensile loading. The water molecules inside a nanoscale tube, unlike inside a bulk tube, have a confined effect. The local density distributions of oxygen and hydrogen atoms inside the carbon nanotubes were calculated to find the confinement effect. Moreover, the mechanical behavior of carbon nanotubes in water was studied under tensile loading. The results show that the Young's modulus of nano-tubes in water remains the same as that in vacuum. However, the tensile stress of nanotube in water is less than that in vacuum.

Tricarboxylic acid derivative with three-fold symmetry in physisorbed monolayers is an important organic molecule for applications in nanotechnology. In this paper, the behaviour of a single tricarboxylic acid derivative, 1,3,5-tris(carboxymethoxy)benzene (TCMB, C6H3(OCH2COOH)3) on an Au (111) substrate at 50 K is investigated by molecular dynamics simulation. Four possible conformations of the TCMB molecule adsorbed on the Au (111) substrate are found, the difference of which is the orientation of the CH2 chain. They also display different trajectories of movement and dynamical behaviours. As the molecule migrates across the Au (111) surface, the translational motion of TCMB is always accompanied by rotational motion. The lock-and-key (LAK) geometry between the TCMB molecule of different conformations and atomic arrangement of the Au (111) surface was also observed in this study, and the result has been verified by an ab initio calculation.

In recent years, the phonon spectrum has attracted much interest in investigations of electric transfer in nanowires. In this study, molecular dynamics is employed to calculate the phonon characteristics of thinness for 7-1 gold nanowire stretched at room temperature. This study finds that the two major peaks of phonon density of state (DOS) of 7-1 nanowire represent low characteristic frequency shifts to the left, while high characteristic frequency is less significant changed compared with the characteristic frequency in bulk. The high frequency intensity of DOS for 7-1 nanowire is lower than that of low frequency. The low frequency shifts left for large elastic strain during elastic deformation. Moreover, the phonon spectrums of one-atom chain structures formed before the nanowire breaks becomes discrete. The influences of local atomic arrangement and stretch condition on the phonon profile are analyzed in this study.

In this study, the molecular dynamics is employed to simulate the selfassembly of crossed gold nanowires at various temperatures. The nanowires with a multi-shell helical (HMS) structure are different from those of the bulk FCC structure. This work compares the morphology of crossed HMS nanowires with 7-1 structure after self-assembly and investigates the atom motion trajectory on the joint. The structure transform are observed from helical structure to FCC structure by angular correlation function (ACF). The results can be suggested for a nano-scale circuit design.

The phonon spectrum has in recent years attracted much interest in investigating electrical transfer in nanowires. In this study, molecular dynamics is employed to calculate the phonon property of thinness for 7-1 gold nanowire at room temperature. This study finds that the phonon density distribution of 7-1 nanowire is different from both that of bulk face-centred cubic (fcc) structure and that of nanoparticles. We also observed that the high frequency of the phonon spectrum in the bulk fcc structure has a higher intensity than the low frequency of the phonon spectrum. This phenomenon, however, does not appear in the 7-1 nanowire. The strain effect of 7-1 nanowire on the phonon property has also been studied; moreover, the phonon spectra of core–core and shell–shell structures of nanowire exhibit two different modes. The relationship between the phonon profile of these core and shell structures is analysed in this study.

Molecular dynamics simulation was employed to investigate the diffusion behaviors of water molecules within a (5,5) carbon nanocoil (CNC) at different tensile strains, the length and coil diameter of CNC are 22 and 6.83 Ǻ, respectively. Condensed-phase, optimized molecular potentials for atomistic simulation studies were employed to model the interaction between atoms. The results show that the diffusion in the axial direction can be enhanced by the tensile strain and the water molecule flow can be blocked at a higher strain once the deformed areas appear at the higher strain. Moreover, the deformed (5,5) CNC at strain of 2.8 can recover its original structure at strain of 0, indicating that the adjustment of diffusion coefficient is repeatable by applying different strains in the axial direction.

This study investigates the behavior of water molecules inside Au nanotubes by molecular dynamics. Different sizes of Au nanotubes under three temperatures for three levels of density of Au nanotube have been studied. The structure of each thermodynamic state is analyzed through the characterization of the hydrogen-bond network. An observation of the water molecule distribution reveals that the adsorption of water molecules creates shell-like formation of water near the Au nanotube wall, and such formations are found to be more pronounced within an Au nanotube. Au atoms of different sizes have an affinity for water molecules at different temperatures.

In this paper, molecular dynamics simulation is carried out to investigate the mechanical properties and dynamic behaviors of carbon nanotubes with vacancies and related defects. We have shown the Yang's modulus and tensile strength of nanotubes with vacancy-related defects are dependent on the characteristics of vacancies. Meanwhile, the phonon density of state (DOS) are used to study the vibration properties of carbon nanotubes of various types. and further determine the dynamical behavior of carbon nanotubes under different tensile strains.

The phonon spectra in 7-1 structure of gold nanowire, which is the simplest structure among possible helical multi-shell nanowire, are studied by using molecular dynamics simulations with a tight-binding many-body potential. Our simulation identifies the outer tube (shell) and inner gold-atom row (core strand) vibrational modes. Generally, atomic interactions have a stiffening force constant due to the shortening the neighbor distance in the interior atoms. The high frequency characteristics of the vibrational modes of core strand are more pronounced than that of outer shell. However, the global phonon density of states (DOS) is predominated by the outer shell modes. The results show that the vibrational frequencies of the ultrathin gold nanowires are dependent on the strain of the wire stretching. The high frequency modes gradually decrease when strain is increased.

Molecular dynamics is employed to investigate the collective motion of carbon atoms of a (10,10) single walled carbon nanotube under tensile loading. The “slip vector” parameter is used to study the collective motion of a group of atoms and deformation behavior in three different directions (axial, tangential, and radial directions). According to the variations in the slip vectors in different directions and the stress-strain profile, the axial tensile process can be divided into three stages. In tensile loading process, two local deformation types (symmetrical and nonsymmetrical deformations) are observed before reaching the maximum stress. The variations in the slip vector values of each atom indicate a symmetrical rupture which is oriented 45° to the axis of the nanotube after reaching the maximum stress. By tensile loading, chainlike structures can be formed before the breaking of the nanotube.

The dynamic behaviour of a multi-shell 14-7-1 Au nanowire is investigated and compared with that of a 7-1 Au nanowire under various tensile strains. The molecular dynamics (MD) simulations performed in this study compute the frequency shift and change in intensity of the characteristic frequency peaks of the phonon density of states of the global and substructure atoms in the radial and axial directions. The results show that the frequency shift and intensity change of the characteristic frequency peaks in the strained 14-7-1 nanowire are caused by a change in the radial atomic coupling and a higher degree of structural anisotropy due to the applied strain.