Both the ionized impurity scattering rate and its angular dependence inn‐type silicon were theoretically calculated using a full band model, in which a wave‐vector‐ and frequency‐dependent dielectric function was used instead of the dielectric constant of 11.7&egr;0. The number of grid points was determined from the relation between the wave vector and screening length to ensure the validity of the ionized impurity scattering rate. The results show that (1) the calculated overlap integral is small compared with the one used in a nonparabolic band model and (2) the screening effect is strong especially for low energy electrons. The validity of the scattering rate was tested by comparing electron mobilities obtained by a full Monte Carlo simulation with experimental data. ©1996 American Institute of Physics.