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Two‐parameter analysis of auxetics among the cubic crystals is proposed. A brief analysis of the equivalence of this two‐parameter consideration and other approaches is given. The main result of this paper is the classification of partial auxetics with a single dimensionless complex, which is composed of the crystals elastic compliances. The auxetic surface separates the regions with negative and positive Poisson's ratio. The character of its changes with change of the dimensionless complex is determined. The critical value of the complex where a topological rearrangement of the auxetic surface occurs is obtained. The distribution of partial auxetics in zones with different values of the dimensionless complex was found. The sign of another dimensionless parameter influences the location of a region with negative Poisson's ratio relative to the auxetic surface. View of the auxetic boundary for a cubic crystal when the dimensionless elastic parameter is close to the critical value Πnormalc≈0.745.

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Mechanical response of the carbon nanotube bundle to uniaxial and biaxial lateral compression followed by unloading is modeled under plane strain conditions. The chain model with a reduced number of degrees of freedom is employed with high efficiency. During loading, two critical values of strain are detected. Firstly, period doubling is observed as a result of the second order phase transition, and at higher compressive strain, the first order phase transition takes place when carbon nanotubes start to collapse. The loading-unloading stress-strain curves exhibit a hysteresis loop and, upon unloading, the structure returns to its initial form with no residual strain. This behavior of the nanotube bundle can be employed for the design of an elastic damper.

Diamond‐like carbon nanostructures with cubic anisotropy made by joining fullerene‐like molecules of different types via valence bonds are studied by means of molecular dynamics simulations. The considered structures are interesting because they include both sp2‐ and sp3‐hybridized carbon atoms, which lead to their distinct properties compared to the structures with one type of hybridization. Seven diamond‐like carbon phases having different shapes of structural units and/or different ways of their connection are studied in the present work. For the relaxed equilibrium structures, the engineering elastic constants (Poisson's ratio, Young's modulus, and shear modulus) are calculated as the functions of the crystal orientation angles. Extreme values of the elastic constants are reported. It is shown that two of the considered diamond‐like structures have negative Poisson's ratio and can be regarded as the partial auxetics. According to the results of the present study, elastic properties of the bulk diamond‐like carbon structures can vary considerably depending on their structure. Diamond‐like carbon nanostructures