A bundle of aligned carbon nanotubes (CNTs) under lateral loading and heating is considered under plane strain conditions within the framework of a molecular dynamics model with a reduced number of degrees of freedom. Bundles of CNTs of sufficiently large diameter exhibit negative lateral thermal expansion. The coefficient of thermal expansion is practically constant up to a temperature of 1500 K and practically does not depend on biaxial lateral compression up to a volumetric compressive strain of 0.06. This anomalous behavior is explained by the two mechanisms: elliptization of the CNT cross section and bending of the CNT walls by thermal fluctuations. Elliptization leads to a decrease in the cross‐sectional area of the CNT, and the bending of the CNT wall leads to a decrease in the effective diameter of the CNT. A bundle with CNTs of the largest investigated diameter demonstrates a large negative coefficient of linear thermal expansion,  K−1, which is weakly dependent on temperature.

Carbon nanotubes (CNTs) have attracted increasing attention because of their enormous potential in various technologies. Herein, the evolution of the structure and elastic properties of a CNT bundle under compression in uniaxial and biaxial regimes is analyzed using a chain model with a reduced number of degrees of freedom. The compression stress–strain curves consist of four stages, each of which is characterized by a specific structure and deformation mechanism. In the first stage, all CNTs have the same cross section; in the second stage, the translational symmetry is preserved in the system, but with a doubled translational cell; in the third stage, CNT collapse takes place, leading to the loss of the translational symmetry; the fourth stage begins when all CNTs collapse. Elastic constants are calculated for the CNT bundle under uniaxial and biaxial compression during the first two stages. In all loading schemes, during the second stage of deformation, the CNT bundle exhibits partial auxetic properties. The results obtained contribute to the fundamental knowledge for the design of carbon nanomaterials with enhanced properties.

The fullerene family, whose most popular members are the spherical C60 and C70 molecules, has recently added a new member, the cube-shaped carbon molecule C8 called a cubene. A molecular crystal based on fullerenes is called fullerite. In this work, based on relaxational molecular dynamics, two fullerites based on cubenes are described for the first time, one of which belongs to the cubic system, and the other to the triclinic system. Potential energy per atom, elastic constants, and mechanical stress components are calculated as functions of lattice strain. It has been established that the cubic cubene crystal is metastable, while the triclinic crystal is presumably the crystalline phase in the ground state (the potential energies per atom for these two structures are −0.0452 and −0.0480 eV, respectively).The cubic phase has a lower density than the monoclinic one (volumes per cubene are 101 and 97.7 Å3). The elastic constants for the monoclinic phase are approximately 4% higher than those for the cubic phase. The presented results are the first step in studying the physical and mechanical properties of C8 fullerite, which may have potential for hydrogen storage and other applications. In the future, the influence of temperature on the properties of cubenes will be analyzed.

This research paper studies the fracture and mechanical properties of rippled graphene containing dislocation dipoles. The atomistic simulation is performed to study the deformation behavior of pristine and defective wrinkled graphene. Graphene wrinkling considerably decreases the ultimate tensile strength of graphene with and without defects but increases the fracture strain. For graphene with the dislocation dipoles, temperature increase slightly affects mechanical properties, in contrast to graphene and graphene with Stone–Wales defect. The extremely similar slopes of the stress-strain curves for graphene with the dislocation dipoles with different arms imply that the distance between dislocations in the dipole does not have noticeable effects on the elastic modulus and strength of graphene. Defects in graphene can also affect its wrinkling; for example, preventing wrinkle formation.