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.

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

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.

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