Bandstructure and optical properties of $\alpha-LiIO_{3}$ crystal

The bandstructure was calculated by the full-potential linearized augmented plane wave method. The result reveals two important insights to the novel second harmonic generation (SHG) of alpha-phase lithium iodate ($\alpha-LiIO_{3}$) crystal: the existence of finite intra-band momentum matrix elements due to the non-inversion symmetry of the crystal illuminating the potential of the intra-band transition, and the strong covalent bonding between the $I$-atoms and the ligand $O$-atoms resulting the condition of the double-resonance. An inter-band transition scenario in SHG as $\alpha-LiIO_{3}$ in nano-structure is proposed. The optical properties were calculated within the theoretical framework of the time-dependent perturbation of the independent-particle model. The dielectric tensors and the refractive index were evaluated. Comparisons between the predictions and the results were made: the x-ray near edge absorption spectra; the refractive index at the static limit, and at finite frequencies. Possible factors attributing the calculation errors is discussed.