some papers mentioned that

"There is no method at present for directly determining the infrared intensities for
vibrational normal modes determined using PBC methods.a method was implemented that uses the Mulliken charge to estimate the change in the
dipole moment.Using the normal mode projections obtained from calculation of the
hessian matrix, this method permits calculation of the dipole derivative required for
estimation of the infrared intensities. The eigenvectors obtained from the normal mode calculation were used to displace the geometry of the molecule. The difference dipole moment (∂μ/∂Q) required for calculation of the infrared transition moment was calculated from the dipole moment in each geometry."

we had got dipole moment and normal mode, how should I do to obtain infrared intensity?

best wishes!