TE-C36 carbon: a new semiconducting phase with an all-sp 3 bonding network.

A new carbon allotrope is investigated by first principles calculations. The allotrope consists of 36 atoms in a tetragonal cell and displays P 4 2 / nmc symmetry (termed TE-C36 carbon) with a mass density of 3.18 g cm -3 . The new carbon phase has an all-sp 3 network, possessing squares, rhombuses, pentagons and hexagons formed by near-by atoms. The dynamic and mechanical stabilities are demonstrated by phonon dispersion and elastic constants, respectively. Its bulk modulus is 353 GPa. The analysis of its electronic band structure shows that it is a semiconductor possessing a direct band gap of 2.25 eV. X-ray diffraction patterns and Raman spectra are also simulated for future experimental characterization. Due to the direct band gap and a comparatively large bulk modulus, this new semiconducting carbon allotrope may possess not only potential electronic and optical applications but also mechanical application.