Structure prediction of ternary Ge-C-N system

The crystal and electronic structures of the Ge-C-N system were calculated by ab initio simulations with the generalized gradient approximation in the density-functional theory. The calculation results show that the lattice constant of the Ge-C-N system decreases monotonously as the C₃N₄ mole fraction increasing. The composition-dependent band gap exhibits as a concave curve and existence of alternations between direct and indirect band gaps. These suggest that the Ge-C-N system with low and high carbon compositions is of potential material for fabrications of optoelectronic devices because of its direct and wide band gap.