Low-temperature phase transformation from nanotube to sp³ superhard carbon phase

Numerous new carbon allotropes have been uncovered by compressing carbon nanotubes based on our computational investigation. The volume compression calculations suggest that these new phases have a very high anti-compressibility with a large bulk modulus (B₀). The predicted B₀ of new phases is larger than that of c-BN (373 GPa) and smaller than that of diamond (453 GPa). All of the predicted structures are superhard transparent materials with a larger band gap and possess the covalent characteristics with sp³-hybridized electronic states. The simulated results will help us better understand the structural phase transition of cold-compressed carbon nanotubes.