BaWO 4 crystals have been obtained by a co-precipitation method, and their structures were characterized by X-ray diffraction and Rietveld refinement techniques, while field emission scanning electron microscopy was utilized to investigate the morphology of the as-synthesized aggregates. Geometries, bulk electronic properties, surface energies, and surface tension of the obtained BaWO 4 crystals were evaluated using first-principles quantum mechanical calculations. A theoretical model based on the Wulff construction was introduced to explain possible crystal morphologies by tuning their surface chemistry, which is related to the relative stability of the faceted crystals. Both the experimental and theoretical data revealed the presence of (112), (001), and (100) facets with low values of surface energy in the BaWO 4 crystals. The experimental morphologies of the as-synthesized samples are similar to the theoretically obtained shapes when surface energy values for the (001) and (100) surfaces are increased simultaneously.

CaZrO3 (CZO) powders were synthesized at different temperatures (400, 600, 800, and 1000 °C) and characterized by X-ray diffraction, Raman and ultraviolet-visible spectroscopic methods, along with photoluminescence (PL) emissions. First principle calculations based on the density functional theory (DFT), using a periodic cell models, provide a theoretical framework for understanding the PL spectra based on the localization and characterization of the ground and electronic excited states.Fundamental (singlet, s) and excited (singlet, s*, and triplet, t*) electronic states were localized and characterized using the ideal and distorted structures of CZO. Their corresponding geometries, electronic structures, and vibrational frequencies were obtained. A relationship between the different morphologies and structural behavior has also been established. Polarized structures were identified by the redistribution of the 4dz2, 4dyz, and 4dxy (Zr) orbitals at the conduction band and the 2pz (O) orbital in the valence band for s, s* and t*. Analysis of the vibrational eigenvector modes of these electronic states reveals a relationship between them via asymmetric bending and stretching modes that arise from Zr atom displacements due to polyhedral [ZrO6] distortion. Furthermore, the results provided an insight into the PL emissions of the as-synthesized CaZrO3 and led to the conclusion that the presence of electronically excited states is strongly related to the structural order-disorder effects (polyhedral distortion) at short range for both [ZrO6] and [CaO8] clusters.

In this study, we present a combined experimental and theoretical study of the geometry, electronic structure, morphology, and photoluminescence properties of CaZrO3:Eu3+ materials.

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A preocupação com o meio ambiente e o modo correto de descarte de corantes têxteis em eflente têm sido tema de vários estudos. A contaminação de águas por corantes industriais é, sem dúvida, um dos problemas atuais não só no Brasil, mas em todo mundo. O objetivo dos pesquisadores acerca deste tema envolve o estudo de Processos Oxidativos Avançados (POAs) que se apresentam como uma potente alternativa de método rápido e efiiente para a completa descoloração de corantes em águas. Neste estudo, realizou-se uma revisão da literatura em torno dos mais novos métodos de descoloração de corantes têxteis.

In this study, quantum-mechanical calculations in the framework of the Density Functional Theory (DFT) were performed to investigate the role of exchange-correlation functional in describing structural, electronic, and magnetic properties of ZnFe 2 O 4 . Herein B3LYP, PBE0, B1WC, and WC1LYP functionals implemented in the CRYSTAL17 code were considered due to the different amounts of the exact Hartree-Fock exchange fraction. In particular, the role of HF fraction on ZnFe 2 O 4 properties was addressed for the first time. Indeed, structural, electronic, and magnetic properties indicate the dependence upon the exchange fraction, where WC1LYP with a 16% exact HF exchange exhibits the best performance compared to the other hybrid functionals. The obtained results reveal an excellent agreement for bandgap, local magnetic moment, long-range magnetic ordering, and unit-cell lattice parameters, overcoming previous theoretical studies based on local/semilocal exchange-correlation treatments. These results confirm the importance of hybrid HF/DFT with controlled HF term contribution to describe the essential features of strongly correlated materials.