Using a semiclassical perturbation approach, we have calculated electron-, proton-, and He III-impact line widths and shifts for 4 Si XI multiplets for perturber densities 10^18^-10^23^cm^-3^ and temperatures T=500000-4000000K, and for 61 Si XIII multiplets for perturber densities 10^16^-10^23^cm^-3^ and temperatures T=500000-6000000K. For lower perturber densities, obtained results are linear with perturber density.