THE INFLUENCE OF THE STACKING-SEQUENCE ON THE ELECTRONIC-STRUCTURE AND OPTICAL-PROPERTIES OF CASI2

The electronic structure and optical properties of CaSi2 have been stu died by the ab initio full-potential and full-relativistic LMTO method s. Calculations are employed to elucidate the influence of the stackin g sequence on the band states and Optical spectra. Unusually strong hy bridization of the Ca spd states with the Si p states is evident in bo th of the crystal polymorphs. The Fermi velocities and charge-density distributions indicate significant spatial anisotropy in the TR3 struc ture. For both of the crystal structures, large in-plane and out-of-pl ane anisotropy of the optical conductivity has also been found.