Mechanical Properties of Phosphorene Nanotubes: A Density Functional   Tight-Binding Study
  Using density functional tight-binding method, we studied the elastic properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nano tubes (PNTs) under uniaxial tensile strain. We found that the deformation and failure of PNTs are very anisotropic. For ZZ PNTs, three deformation phases are recognized: The primary linear elastic phase, which is associated with the interactions between the neighboring puckers, succeeded by the bond rotation phase, where the puckered configuration of phosphorene is smoothed via bond rotation, and lastly the bond elongation phase, where the P-P bonds are directly stretched up to the maximally allowed limit and the failure is initiated by the rupture of the most stretched bonds. 
V. Sorkin and Y.W. Zhang
cond-mat.mes-hall