Ima2 C32: An orthorhombic carbon allotrope with direct band gap

Ima2 C-32 with sp(2) + sp(3) hybridized network is proposed in this work, and the structural properties, electronic properties, absorption spectra, elastic properties, elastic anisotropy properties, and stability of Ima2 C-32 are studies by density functional theory. Ima2 C-32 is dynamically stable, thermodynamically stable, and mechanically stable. The shear modulus and bulk modulus, and Young's modulus of Ima2 C-32 is 217 GPa, 267 GPa, and 512 GPa, respectively, all them are smaller than that of diamond, while Young's modulus, shear modulus and bulk modulus of Ima2 C-32 is larger than that of C24-C and C24-D in sp(2) + sp(3) hybridized structures. Ima2 C-32 is a direct and wider band gap semiconductor material. The visible light absorption ability of Ima2 C-32 is slightly better than C24-D, cubane-yne, and T carbon. Due to the direct band gap and the stronger visible light absorption ability, Ima2 C-32 might be used in the optoelectronic devices. In addition, the elastic anisotropy properties of Ima2 C-32 are also investigated in this work. The Poisson's ratio are negative in (0 0 1), (1-1 0), (1 1 0), (1 0 1), and (1 1 1) planes.