A new parametric method that approximates the radiative accelerations of bound-bound and bound-free transitions at large optical depths is presented. The parameters found in these new equations are calculated for the following trace elements: C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, and Fe and are made available to potential users. This method can be easily implemented in existing codes to study atomic diffusion without needing large computing resources or access to large atomic and opacity data bases.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html