I212121 carbon: An orthorhombic carbon allotrope with superhard properties

An I2₁2₁2₁ carbon with an I2₁2₁2₁ space group and an sp3 hybridized network are proposed in this work. We conduct a comprehensive investigation of I2₁2₁2₁ carbon using density functional theory, including its structure, elastic properties, elastic anisotropy in elastic moduli, electronic properties, stability, absorption spectra, and X-ray diffraction patterns. Our results show that I2₁2₁2₁ carbon is both mechanically and dynamically stable. The calculated elastic moduli (shear modulus G, bulk modulus B, and Young’s modulus E) of I2₁2₁2₁ carbon are 352 GPa, 325 GPa, and 776 GPa, respectively, which are higher than those of Ima2 C32, Penta-C₂₀, C24-C, and C24-D. I2₁2₁2₁ carbon has a wide indirect bandgap and is identified as a semiconductor. The absorption ability, of I2₁2₁2₁ carbon is slightly superior performance compared to C24-D, T carbon, C24-C, Y carbon, cubane-yne, C10-C, C14-C, and C20-D. I2₁2₁2₁ carbon could be used as an ultraviolet detector. In addition, the elastic anisotropy in the elastic moduli and X-ray diffraction patterns of I2₁2₁2₁ carbon were analyzed.