The electronic structure and properties of the orthorhombic phase of the $\mathrm{CH}{}_{3}\mathrm{NH}{}_{3}\mathrm{PbI}{}_{3}$ perovskite are computed with density functional theory. The structure, optimized using a van der Waals functional, reproduces closely the unit cell volume. The experimental band gap is reproduced accurately by combining spin-orbit effects and a hybrid functional in which the fraction of exact exchange is tuned self-consistently to the optical dielectric constant. Including spin-orbit coupling strongly reduces the anisotropy of the effective mass tensor, predicting a low electron effective mass in all crystal directions. The computed binding energy of the unrelaxed exciton agrees with experimental data, and the values found imply a fast exciton dissociation at ambient temperature. Also polaron masses for the separated carriers are estimated. The values of all these parameters agree with recent indications that fast dynamics and large carrier diffusion lengths are key in the high photovoltaic efficiencies shown by these materials.

We examine the dependence on size distribution of the Raman line shape of optical vibron modes in CdSe dots. A detailed comparison with the theory of electron-hole correlated Raman scattering in spherical quantum dots, which includes LO-confined modes, is carried out. The obtained CdSe vibron frequencies are found to map well on the ab initio calculated LO phonon dispersion relations of wurtzite CdSe along the [001] direction of the Brillouin zone.

The electronic structure of bulk $\gamma$-alumina is investigated using Density Functional Theory. Recent theoretical structures, including occupation of nonspinel positions, are used as starting point for energy minimization, allowing for relaxation of the cell shape and the ionic positions. A comparison of simulated diffraction patterns of the present and recent theoretical and experimental structural models is presented. The electronic structure is described in terms of band structure, density of states, charge density, electron localization function, and ionic charges. The valence band density of states of $\gamma$-alumina is similar to $\alpha$- and $\kappa$-alumina, although a smaller bandgap is found. It is shown that $\gamma$-alumina ionicity is similar to other alumina phases, with a high localization of the electrons at oxygen atoms. The smaller bandgap of $\gamma$-alumina is attributed to the structural disorder.

In this study, we report on the structural and hyperfine properties of Al-doped SnO ₂ nanoparticles synthesized by a polymer precursor method. The x-ray diffraction data analysis carried out using the Rietveld refinement method shows the formation of only rutile-type structures in all samples, with decreasing of the mean crystallite size as the Al content. A systematic study of the unit cell, as well as the vicinity of the interstitial position show strong evidence of two doping regimes in the rutile-type structure of SnO ₂ . Below 7.5 mol% doping a dominant substitutional solution of Al ⁺³ and Sn ⁴⁺ -ions is determined. However, the occupation of both substitutional and interstitial sites is determined above 7.5 mol% doping. These findings are in good agreement with theoretical ab initio calculations.