Equilibrium diamond-like carbon nanostructures with cubic anisotropy: Elastic properties

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 sp(2)- and sp(3)-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. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim