Ab initio structural simulation and electronic structure of amorphous carbon

Within the framework of density-functional theory, a new and more accurate exchange correlation functional OLYP(OPTX + LYP) was used to simulate the structures of amorphous carbon at densities from 2.0 to 3.2 g/cm(3). The radial distribution function and sp(3) fraction of the five simulated carbon networks are in good agreement with experimental results. The calculated electronic structures indicate that the states near Fermi level are mainly contributed by sp(2) carbon atoms. The states near Fermi level have a decreasing trend with increasing density and increasing sp(3) content. The small ring structure increases the density of states near Fermi level. The defects will give a peak at Fermi level, which strongly reduces the band gap.