A simple quantum mechanical model is presented for hydrocarbons. It is
a modified version of the model of Davidson and Pickett [Phys. Rev. B
49, 11 253 (1994)]. Self-consistency is introduced through the imposi
tion of local charge neutrality, which is appropriate for hydrogen and
carbon based systems due to the small amount of charge transfer that
takes place. Further, some parameters have been refitted to give the c
orrect binding energies as well as forces. The model is found to give
excellent agreement with experiment and other calculations for hydroca
rbon molecules and the hydrogenated surface of diamond, demonstrating
its transferability.