Two-Dimensional Black Phosphorus Carbide: Rippling and Formation of Nanotubes

The allotropes of a new layered material, phosphorus carbide (PC), have been predicted recently, and a few of these predicted structures have already been successfully fabricated. Herein, by using first-principles calculations, we investigate the effects of rippling an alpha-PC monolayer, one of the most stable modifications of layered PC, under large compressive strains. Similar to phosphorene, layered PC is found to have the extraordinary ability to bend and form ripples with large curvatures under a sufficiently large strain applied along its armchair direction. The band gap, work function, and Young's modulus of a rippled alpha-PC monolayer are predicted to be highly tunable by strain engineering. Moreover, a direct-indirect band gap transition is observed under compressive strains in the range from 6% to 11%. Another important feature of the alpha-PC monolayer rippled along the armchair direction is the possibility of its rolling to a PC nanotube (PCNT) under an extreme compressive strain. These tubes of different sizes exhibit high thermal stability, possess a comparably high Young's modulus, and a well tunable band gap which can vary from 0 to 0.95 eV. In addition, for both structures, rippled alpha-PC and PCNTs, the changes of their properties under compressive strain are explained in terms of the modification of their structural parameters.