Behaviour of radiative accelerations in stars

Diffusion processes are able to stratify elements in stars on time-scales s horter than the evolution time on the main sequence. According to the effic iency of these diffusion processes, which depend on the radiative accelerat ions, abundances are time-dependent and inhomogeneous outside the stellar c ore. Large atomic and opacity data bases allow accurate computations of rad iative accelerations, and several authors have developed efficient methods taking advantage of these large data bases. In the present work, these powe rful tools are used to improve our knowledge on how radiative accelerations depend on the abundances of elements in stellar plasma. In this study, we test the behaviours of radiative accelerations that are u sually supposed. The results we obtain give some clues for future attempts to simplify the calculations of these accelerations.