A Monte Carlo program for simulating plasma ions incident on a surface with a floating potential is presented. This program is used for calculating sputtering, backscattering, and implantation values for deuterium plasma ions incident on a carbon surface. Sputtering, backscattering, and implantation by accelerated Maxwellian, monoenergetic, and Maxwellian ions are compared at the same average incident energy. Values for accelerated Maxwellian ions are found to be significantly different from values for monoenergetic and Maxwellian ions.