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The physical, electronic and optical properties of Barium halides have been investigated by both experimental and theoretical approaches. The First Principle electronic structure and optical properties were calculated by DFT formalism using Full Potential Linearized Augmented Plane Wave plus local orbitals (FP-LAPW + lo) implementing different appropriate exchange-correlation functionals in WIEN2k code at various applied volumetric pressure up to 50 GPa. All the properties of these halides were analyzed and compared using their cation-anion radii ratio and ionicity. Except BaF 2 , the other three halides show ionic to covalent transformation at 50 GPa applied pressure. Both experimental and theoretical results compare reasonably well. The scintillation efficiency of these three halides was found to be directly proportional to their ionicity or band gap. • Study of physical, electronic and optical properties of Barium halides by experimental and theoretical approaches. • All the properties of the halides were analyzed and compared using their cation-anion radii ratio and ionicity. • The direct type band gap of the three halides decrease with pressure at least till 50 GPa. • Observed ionic to covalent transformation at 50 GPa applied pressure. • Experimental and theoretical results match reasonably well. [ABSTRACT FROM AUTHOR]

The short-wavelength sub-nanosecond luminescence in BaF 2 material, discovered in the early 80s, gave a new direction to research into fast scintillators and phosphors. In contrast to 'typical' luminescence occurring within the forbidden band gap, the new type of emission was due to transitions between the upper core and valence bands. Thus it was named core-valence luminescence (CVL); the terms cross-luminescence and Auger-free luminescence have also been used. Given its unusual nature, this new luminescence process has attracted considerable interest in the field of condensed matter physics. During the sequent decades (till the end of the previous century) CVL has been experimentally observed in several dozen compounds and the conditions for detecting CVL have been established. Interest in this kind of luminescence increased in recent years due to the emergence of new methods of crystal synthesis, the development of high-speed solid-state photodetectors, and the construction of unique modern set-ups using synchrotron radiation. This paper analyzes the numerous studies of CVL, obtained mainly over the past decade. Experimental and theoretical data on this topic are considered in detail. Special attention is given to new results on scintillation characteristics of BaF 2 in the form of single crystals, ceramics, nanoparticles, and composites. The features of CVL in binary and ternary compounds are discussed. Some Cs- and Ba-based ternary halides show relatively high light yields and represent promising fast scintillators. The prospects of using materials with CVL as fast scintillators for time-of-flight positron emission tomography and other applications are deliberated. • Overview of recent theoretical and experimental findings on Core Valence luminescence. • Most attractive CVL crystals for ultrafast scintillator applications analyzed. • Prospects for future studies and underexplored CVL materials listed. [ABSTRACT FROM AUTHOR]