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 (B-0). The predicted B-0 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 sp(3)-hybridized electronic states. The simulated results will help us better understand the structural phase transition of cold-compressed carbon nanotubes.