We consider optically active photonic crystals. We propose a model structure and discuss the factors which determine optical activity by reference to this model.

We report systematic calculations of the low-temperature diffusion thermopower of Al-based dilute alloys with 3d and 4sp impurities, by solving self-consistently the linearized Boltzmann equation. The impurity scattering is described by the phase shifts obtained from self-consistent local-density-functional impurity-in-jellium calculations. Moreover, the influence of the full anisotropy of the Al Fermi surface on the scattering process is taken into account within the on-Fermi-sphere approximation. Our results explain successfully the experimentally measured variations in the thermoelectric power, except for Mn impurities. In this case, the presence of a narrow many-body resonance at the Fermi level in the localized spin-fluctuations regime seems to be responsible for the large negative value of thermopower observed.

We present density-functional calculations within the local-density approximation for all transition-metal impurities in the divalent hosts Ca, Sr, and Ba. Our results predict sizable moments, even for impurities of the 4d and 5d series, being only slightly smaller than the moments obtained in the corresponding alkali metals