Theoretical Investigations of the Hexagonal Germanium Carbonitride.

The structural, mechanical, elastic anisotropic, and electronic properties of hexagonal germanium carbonitride (-GeCN) are systematically investigated using the first-principle calculations method with the ultrasoft pseudopotential scheme in the frame of generalized gradient approximation in the present work. The -GeCN are mechanically and dynamically stable, as proved by the elastic constants and phonon spectra, respectively. The -GeCN is brittle because the ratio / and Poisson’s ratio of the -GeCN are less than 1.75 and 0.26, respectively. For -GeCN, from brittleness to ductility, the transformation pressures are 5.56 GPa and 5.63 GPa for / and Poisson’s ratio , respectively. The -GeCN exhibits the greater elastic anisotropy in Young’s modulus and the sound velocities. In addition, the calculated band structure of -GeCN reveals that there is no band gap for -GeCN with the HSE06 hybrid functional, so the -GeCN is metallic.