  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.
