First-principles calculation of the mechanical properties of diamond nanothreads

The synthesis of novel one-dimensional carbon nanostructures named diamond nanothreads (DNT) has been recently reported, and subsequent studies employing molecular dynamics (MD) simulations demonstrated that they possess remarkable mechanical properties. In this paper we present the results of Density Functional Theory calculations of the mechanical properties for several DNT configurations, confirming that they indeed exhibit a high ideal strength (as high as 15.7 nN or 2.6 x 10(7) N m/kg) and stiffness (as high as 168 nN or 2.8 x 10(8) N m/kg), similarly to other carbon nanostructures. We compare these results with previously reported and additional MD calculations, and show that traditional interatomic potentials predict these properties with deviations up to similar to 50%. A detailed analysis of the dependence of atomic structure on strain shows the reasons for these discrepancies. We also show that the most known DNT configuration (the (3,0) sp(3)-nanotube) exhibits a negative radial Poisson ratio. (C) 2016 Elsevier Ltd. All rights reserved.