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A forest of oriented carbon nanotubes (CNTs) is considered under lateral loading and heating under planar deformation using the molecular dynamics method with a reduced number of degrees of freedom. It is shown that a CNT forest of a sufficiently large diameter has a negative coefficient of transverse thermal expansion. The thermal expansion coefficient weakly depends on temperature in the range up to 1500 K and practically does not depend on the volumetric compression deformation up to 0.06. This effect is explained by the elliptization of the CNT cross section and warping of the CNT walls by thermal vibrations. Elliptization, while maintaining the CNT cross-section length, leads to a decrease in the cross-sectional area of the CNT, and the warping of the CNT wall leads to a decrease in the effective diameter of the CNT. [ABSTRACT FROM AUTHOR]

Using of molecular dynamics modeling, the effects of temperature on the movement of dislocations in graphene are studied for several types structural defects - Stone-Wales (or a dipole with a zero shoulder) and dislocation dipoles 5-7 with arm lengths 7, 9.3, and 11.5 Å. It is found that dislocation dipoles remain stable at temperatures below 1400 K. An increase in temperature leads to the movement of dislocation dipoles either towards each other (typical for all studied dipoles), or in the opposite direction (only for dipoles with arm lengths of 9.3 and 11.5 Å). When dislocations move towards each other, their annihilation can occur due to a simple rotation of the C-C bond. It is shown that the arm length 9.3 Å is close to the equilibrium value at which dislocation annihilation is not observed. [ABSTRACT FROM AUTHOR]

One-component delocalized nonlinear vibrational modes (DNVM) are investigated by the molecular dynamics method. DNVMs are obtained by considering exclusively the symmetry of the triangular lattice, and thus they exist regardless of the type of interactions between particles. In this work, interparticle interactions of the nearest neighbors are described by the β-FPU potential. The possibility of the appearance of a discrete breather in a system with a soft and hard type of nonlinearity is studied, and the dependences of the frequency on the amplitude are plotted. The data obtained expand our understanding of nonlinear oscillations in the studied one-component modes. [ABSTRACT FROM AUTHOR]

The deformation behavior of tubulanes or diamond-like phases composed of carbon nanotubes is studied by molecular dynamics. Six stable tubulanes with different morphologies are studied under hydrostatic loading. It is found, that the deformation process can be divided into three main parts - elastic deformation, inelastic and pre-critical deformation. During the elastic regime, commonly, stretching of the covalent bonds is the main deformation mechanism for conventional materials. The inelastic regime can be also divided into several regions in accordance with the leading deformation mechanism. In the pre-critical stage, a sharp decrease of stress is observed, which indicates the critical moment and subsequent failure. The leading deformation mechanism is defined by the structural peculiarities and can be different for six phases, although qualitatively, the mechanical behavior of all phases is similar. [ABSTRACT FROM AUTHOR]