First-principles calculations of structural, electronic and optical properties of orthorhombic CaPbO3

Calculations within the density functional theory approach were performed to obtain structural parameters, electronic band structure, carrier effective masses and optical absorption spectra in orthorhombic CaPbO3. Both local density and generalized gradient approximations, LDA and GGA, respectively, were considered. A comparison reveals good agreement of the calculated lattice parameters with experimental results. A direct Gamma ->Gamma one-electron energy band gap of 0.84 eV (0.94 eV) was obtained within the GGA (LDA) level of calculation, in contrast to a previous interpretation of experimental data pointing to a gap of only 0.43 eV. Comparting our results with band gap energies previously obtained for CaXO3 crystals (X = C in calcite, X = Si in wollastonite and X = Ge, Sn, Pb in the orthorhombic phase), we note that the energy gap oscillates, but with an overall trend to decrease, as the atomic number of the X atomic species increases.