Tight-binding molecular-dynamics study of amorphous carbon

The structural and electronic properties of amorphous carbon are studied with tight-binding molecular-dynamics simulations. An amorphous carbon structure with 216 atoms obtained from our simulation gives a structure factor S(Q) in very good agreement with the results of neutron scattering from a sputtered a-C sample. We found that the amorphous structure consists of graphitelike fragments embedded in a matrix of both twofold and fourfold coordinated atoms. We also found a small pseudogap in the electronic density of states at the Fermi level.