Electronic and optical competence of TiO2/BiVO4 nanocomposites in the photocatalytic processes.

Nanocomposites with different ratios of titanium dioxide and bismuth vanadate [TiO2]/[BiVO4] give rise to compatible electronic band structure alignment at their interfaces to ensure enhanced photoactivated charge transfer under visible light. The sol-gel method and suitable post-synthesis thermal treatments were used to synthesize different compositions with stabilized anatase phase of TiO2 and monoclinic scheelite polymorph BiVO4. Structural, electronic and optical characterizations were performed and the results were analysed as a function of the stoichiometry, in which both crystalline structures show a clear junction formation among their characteristic stacking planes. Photocatalytic and (photo) electrochemical responses of the nanocomposites were investigated and tested for the degradation of azo dyes (Acid Blue-113, AB-113) (~ 99%) under visible light radiation. The nanocomposite with a mass ratio of (1:10) shows the highest photocatalytic efficiency compared to the other compositions. HRTEM images showed marked regions in which both crystalline structures form a clear junction and their characteristic planes. However, the increase of BiVO4 content in the network overcomes the photocatalytic activity due to the decrease in the reduction potential of the photo-generated electrons with high recombination rates.

Comparing two high correlation models to test the mechanical stability of americium-II.

In this work two high density functional theory (DFT) correlation methodologies, the so called DFT+U (or GGA+U) implementation and the exact exchange of correlated electrons (EECE), hybrid DFT functional (or one case of hybrid DFT), are tested to determine the mechanical properties of americium-II. For each case, the numeric value of their principal parameter is chosen ([Formula: see text] for the first case and [Formula: see text] for the second one) once the crystalline structure meets all the mechanical stability conditions. The results show that there is a range of values of [Formula: see text] and [Formula: see text] in which both methodologies generate a stable (experimentally correct) non-magnetic ground state, reaching approximately the same numeric value of the set of elastic constants of the cubic structure. However, only for the case of the hybrid functional results it is possible to show how the non-magnetic configuration is energetically favored, as compared to the ferromagnetic configuration. This happens around [Formula: see text], a value in agreement with a previous analysis made under the same methodology for the metal case Am-I. Following a detailed and deep analysis, it is possible to find a close interrelation between the electronic properties of the metal: its distribution of states around the Fermi level, the energy difference between the two possible spin configurations, and the mechanical response of the crystal. Also, it is possible to conclude that the effect of alpha parameter on the [Formula: see text] electrons can be used as a parameter to simulate the presence of an external pressure over the structure. For the comparison, the calculations were performed within the LAPW approximation in DFT as implemented in the WIEN2k code, with a finite deformation method.