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The spectroscopic properties of the Mn4+ ion are investigated in the series of isostructural double perovskite compounds, Ba2BTaO6 (B = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B3+–Ta cations on the energy and intensity of the Mn4+2E → 4A2 emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy. The influence of covalent bonding within the corner shared BO6/2 and TaO6/2 perovskite framework on the energy of the R-line energy is investigated. From the spectroscopic data, we have derived information on the influence of the degree of order between the B3+ and Ta5+ cations on the intensity of the R-line. The lowest energy and the highest intensity of the R-line are found in the double perovskite, Ba2ScTaO6. The purpose of this work is to propose for first time an explanation of these effects in the considered double perovskites. The obtained results are useful guidelines for practical improvement and tuning of key parameters of phosphors to the desired values.

Fast development of computer facilities and quantum chemical calculations made computational materials science be a very important tool in modern research aimed at design, development and understanding of novel functional materials with enhanced performance. This special issue is focused on applications of various computational methods to the description of physical properties of optical materials. Density Functional Theory (DFT)-based computational techniques, semiempirical crystal field models, machine learning and other tools used for explanation of experimental results, deeper understanding of optical materials properties and smart search for new materials with advanced characteristics are discussed in the special issue papers. All authors of these selected papers are well-known scientists who made solid contributions to their respective fields of research. Wide range of presented methods and approaches, together with broad scope of the considered materials and phenomena (phosphors, optical thermometers, radiative and non-radiative transitions) will make this collection of papers an interesting and valuable source of scientific information for an audience ranging from postgraduate students to experienced researchers

A comparative study of Eu3+ luminescence in an isostructural series of phosphate and vanadate compounds correlates the hypersensitivity of the 5D0→7F2 transition to the covalence and polarizability of the (XO4)3- (X = P, V) polyanion. The intensity of this transition, as measured by the ratio, [Formula presented], is always higher in the vanadate system [R (PO4)3-« R (VO4)3-]. Electronic energy band structure of these systems establishes higher covalence and polarizability of the (VO4)3- polyanion, which is due to strong V 3 d - O 2p covalent interaction via hybridization. The difference in the intensity of the hypersensitive transition between the phosphate and vanadate systems is consistent with the prediction of the ligand dipolar polarization model for the 4f-4f dipolar intensities. Our analysis supports the polarizability of (XO4)3- (X = P, V) over local site distortion effects as the intensity enhancing mechanism of the 5D0→7F2 transition. It is pointed out that the hybridization effect that serves as the source of the intensity of hypersensitive transition also accounts for the origin of second harmonic generation (SHG) in Li3VO4 and its absence in Li3PO4. © 2023 Elsevier B.V.