Comparison of empirical potentials for calculating structural properties of amorphous carbon films by molecular dynamics simulation

Amorphous carbon (a-C) films were deposited by molecular dynamics simulation using Tersoff, REBO and AIREBO potentials, respectively. The hybridization and the distributions of both bond angles and lengths as a function of the three potentials were analyzed, and the density and residual stress were calculated. Results revealed that comparing with the Tersoff and REBO potentials, the AIREBO potential gave the more reasonable values of density, hybridization ratio and residual stress. This attributed to that in AIREBO potential, the conjugation effect between the different coordinated atoms was corrected by revising the bond order term, which was responsible for the sp(3) content; while the introduction of long-range Lennard-Jones (LJ) interaction described the compressed graphite structure correctly following the rational density; in particular, both the LJ and torsion interactions were indispensable for the accurate evaluation of residual stress of a-C films. In addition, the simulation result using AIREBO potential suggested no dependence on the processing methods of atom-by-atom deposition and liquid-quenching method.