Simulation of amorphous carbon with a bond-order potential

Simulations of amorphous carbon were performed at densities ranging from 2.0 to 3.0gcm 3 with a reactive bond-order potential. The fraction of sp 3 bonding increases with increasing density, as is observed experimentally, but with generally too much sp 2 content. Ring size distributions are calculated, with a number of large rings observed. It is suggested that structural quantities that are more directly related to physical properties—such as void volumes and coordination numbers—are more useful than ring size distributions in characterizing the structure of amorphous carbon. Void fractions and void volume distributions are calculated, indicating that a percolating void network exists at 2.0gcm 3 , large, non-percolating voids exist at intermediate density, and no voids are found larger than atomic volumes at 3.0gcm 3 .