Electronic and optical properties of CaCO₃calcite, and excitons in Si@CaCO₃and CaCO₃@SiO₂core-shell quantum dots

Density functional theory calculations of the electronic and optical properties of the CaCO 3 calcite polymorph were performed within both the local density (LDA) and generalized gradient (GGA) approximations, respectively. The carriers effective masses are estimated, and the energy gap is shown to be indirect, with and (for comparison, the experimental value is 6.0 ± 0.35 eV). Two optical absorption regimes are predicted, and the dielectric function does not change considerably with the light polarization. The confinement features of excitons in Si@CaCO 3 and CaCO 3 @SiO 2 spherical core-shell quantum dots are also presented.