Improved hydrocarbon potentials for sputtering studies

We refit the REBO hydrocarbon potentials by reparameterizing the bond lengths and energies of hydrocarbons with recent data, using systematic addition of the parameters of all hydrocarbons CxDy with x equal or less than four. In addition we also refit the short-distance potentials to reproduce a repulsive ZBL term. To test the improved potential, we performed large scale molecular dynamics calculations of amorphous deuterated carbon bombarded by deuterium, and compare our results with data obtained using the REBO potential as well as with recent experiments.