# Classical electrodynamics¶

GPAW can perform classical electrodynamics simulations using quasistatic finite-difference time-domain (QSFDTD) method. In these calculations you must specify the regions with classically polarizable material, as well as their permittivities $$\epsilon(\mathbf{r}, \omega)$$. The electric field and the polarization charge density are propagated in time under an influence of external perturbation. The QSFDTD method can be also merged with time-propagation simulation, which yields a hybrid multiscale method.