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Truncated carbon nanocones (CNCs) can be taken as energy suppliers because of their special structures. In this paper, we demonstrate the stability of truncated CNCs under compression and the escape behavior of a fullerene catapulted from a compressed CNC by molecular dynamics simulations and theoretical models. The strain energy of a CNC and cohesive energy between a fullerene and the CNC (due to their van der Waals interactions) dominate the stability and catapulting capability of the cone, which strongly depend on geometrical parameters (apex angle, top radius and height) of each CNC and axial distances between them. In particular, the additional transverse vibration of buckled CNCs after released plays a significant role in their catapulting abilities and efficiencies. Finally, finite element method and experiments are further performed to validate the escape mechanism. This study should be of great importance to providing a theoretical support for designing novel nanodevices in mico/nanoelectromechanical systems.

Buckling behaviors of single-walled carbon nanotubes (SWCNTs) inserted with a linear carbon-atom chain (CAC) (the composite structures are also called carbon nanowires (CNWs)) under torsion and bending as well as compression are studied using molecular dynamics (MD) simulations, respectively. Our MD results show that the critical buckling angles (or strains) of CNWs under the three presented kinds of loading patterns can be two times those of corresponding independent SWCNTs for long CNWs, while the buckling improvement is not obvious for short ones. The main reason is that the radial van der Waals force between the CAC and the SWCNT is very small for a short CNW, while it increases with increasing length and then tends to a constant for a long CNW. The obtained MD results agree well with those from available theoretical models. These findings will be a great help towards understanding the stability and reliability of the special CNT structures, and designing flexible CNT-based devices.

The failure modes of ZnO nanowires (NWs) with hexagonal cross section subjected to a uniaxial load are systematically investigated by using molecular dynamics (MD) simulations and two theoretical models considering the surface effect. Our results show that two different failure modes of the phase transition and buckling are triggered when the NWs are under uniaxial compression along the [0001] direction, in which the transformation between the two modes is related to the slenderness ratios of the NWs. Such slenderness-ratio-dependent mode transformation is mainly attributed to the competition between the critical stresses of phase transition and buckling. The Euler and Timoshenko models considering surface effect are further proposed to derive the critical slenderness for such mode transformation. The obtained analytical threshold values agree well with those of present MD simulations. Our results should be of great help for shedding some light on the design and application of functional devices based on ZnO NWs.

We show that the hexagonal structure of single-layer molybdenum disulphide (MoS2), under uniaxial tension along a zigzag direction for large deformations, can transfer to a new quadrilateral structure by molecular dynamics (MD) simulations when the temperature is below 40 K. The new phase remains stable after unloading, even at room temperature. The Young's modulus of the new phase along the zigzag direction is about 2.5 times higher than that of normal MoS2. Checking against density functional theory calculations shows that the new phase is preserved and displays excellent electrical conductivity. Our results provide physical insights into the origins of the new phase transition of MoS2 at low temperatures.

We perform both classical molecular dynamics simulations and beam model calculations to investigate the Young's modulus of kinked silicon nanowires (KSiNWs). The Young's modulus is found to be highly sensitive to the arm length of the kink and is essentially inversely proportional to the arm length. The mechanism underlying the size dependence is found to be the interplay between the kink angle potential and the arm length potential, where we obtain an analytic relationship between the Young's modulus and the arm length of the KSiNW. Our results provide insight into the application of this novel building block in nanomechanical devices., Nanotechnology, accepted (2013)

The mechanical properties of supergraphene, cyclicgraphene and graphyne are studied using molecular dynamics simulations based on the AIREBO potential. In particular, we present the chirality-dependence of their mechanical properties, including Young's moduli, shear moduli, Poisson's ratios, ultimate strength and ultimate strains. The relationship of their Young moduli, shear moduli and Poisson ratios is in the order of Y(su) (super)Y(cy) (cyclic)Y(gy) (graphyne)Y(ge) (graphene), G(su)G(cy)G(gy)G(ge) and v(su)v(cy)v(gy)v(ge) in corresponding zigzag and armchair sheets, respectively. Their intersheet adhesion energy is obtained as γ(su) = 30, γ(cy) = 99 and γ(gy) = 149 mJ m(-2), which are much lower than that of γ(ge) = 291 mJ m(-2) (the value is in good agreement with the latest experimental result γ(ge) = 310 ± 30 mJ m(-2)). The obtained adhesion energy is accurately characterized by continuum modeling of the van der Waals interactions. Our study is very useful for the future applications of graphene-like materials in nanoelectromechanical systems.