Improvement of the repulsive part of the classical interatomic potential for SiC

In order to enable a better description of ballistic and athermal processes occurring in the initial stage of ion-beam-induced defect formation, the repulsive part of the interatomic potentials of Gao and Tersoff is improved. The first modification concerns the two-body part of the potentials. At small interatomic distances it is replaced by the well-tested potential of Ziegler, Biersack, and Littmark (ZBL). For repulsive interactions between zero and some ten electron volt, an exponential spline function is employed to connect the ZBL potential with the two-body parts of the Tersoff and the Gao potential. The modified two-body potentials and their first derivatives are continuous and monotonic over the whole range of repulsive interaction. They are in good agreement with data obtained by density-functional-theory calculations. Furthermore, the three-body part of the Tersoff and the Gao potential is modified in order to avoid the strong dependence of repulsive interactions between two atoms on the bond-order parameter, i.e. on their coordinations. The modification is performed in such a manner that the total potential and its first derivative remain continuous and monotonic for all repulsive interactions.