Abstract
We review a real-time computational method for photoionization in molecules based on the time-dependent density-functional theory in linear response regime. In the method, an impulsive external field is applied to a molecule, and the induced electric polarization in the molecule is calculated as a function of time. Then the frequency-dependent polarizability, which characterizes linear optical properties of molecules, is obtained as the ratio between Fourier transform of the induced polarization and that of the applied impulsive field. After presenting the formalism, we explain practical aspects of the procedure taking ethylene and fullerene molecules as examples. We also explain extensions of the real-time formalism for other optical properties such as magnetic circular dichroism, a linear optical property of molecules under a static magnetic field, and dielectric function of periodic bulk materials.
