A superhard incompressible carbon allotrope with deformation-induced transformation to diamond.

Recognizing the indispensability of hard materials in industrial applications, the persistent pursuit of ultra-strong and superhard materials has been a subject of extensive research. Carbon, with its versatile hybridization possibilities, emerges as a promising avenue for the creation of such materials. Herein, based on first-principles calculations, we predict an all- hybrid orthorhombic carbon allotrope named C. It exhibits greater incompressibility along the [010] direction than diamond, demonstrating an extreme hardness with Vickers hardness of up to 72.8 GPa. The Young's modulus of C displays anisotropy, closely comparable to diamond along the x axis direction, while maintaining excellent mechanical stability within the range of 100 GPa. Notably, under the influence of shear force, it undergoes transformation into diamond. Functioning as a transparent semiconductor with a wide indirect band gap of 4.55 eV, C holds promise as a potential superhard material in the semiconductor industry, especially under extreme conditions.