First-principles molecular dynamics study on structural and electronic properties of amorphous germanium carbide

We study the structural and electronic properties of amorphous GeC alloy using the first-principles molecular dynamics simulation. With melting-quenching technique, we obtain the microscopic atomic structure of amorphous GeC alloy from a 2 × 2 × 2 supercell of zinc-blende (ZB) GeC cubic cells. Obvious phase separation is found in the final amorphous structure. The average partial coordination number, average total coordination number, and average bond length are deduced from the RDFs of our structure, and 4.33 and 3.59 coordinations are obtained for Ge and C respectively. Average bond length of 1.46 Å, 2.02 Å, and 2.55 Å are calculated for C-C, Ge-C, and Ge-Ge, respectively. The bond angle distributions are analyzed for different types and great deviation from the ZB structure (109.47°) is observed. The density of states of our modeling shows that the disorder and defects in amorphous GeC have an important effect on the electronic properties. Besides the original sp³ hybridization, new sp² and p-orbital bonding characters of Ge and C atoms are also found.