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Optical absorption measurements were carried out at room temperature on stoichiometric and well characterized vacuum evaporated ZnI2 films as function of film thickness and heat-treatment temperatures. The films were transparent and tetragonally structured. X-ray diffraction analysis reveals residual strain on the crystal planes parallel to film thickness. Optical absorption shows three distinct peaklike structures at 3, 3.5 (attributed to be excitonic), and 4.1 eV. The residual strains as well as all the absorption structures vary with film thickness and treatment temperatures. Combining all the data from the two experiments, we find that the two excitonic peaks blueshift with residual strain of (104). The strain-free values for all the above quantities have been determined by the extrapolation of their linear dependence on residual strain. The excitonic absorption observed at room temperature shows a large excitonic binding energy of 150 meV. [ABSTRACT FROM AUTHOR]

The BaBr 2 films grown by vacuum thermal evaporation prefer three different completely ( hkl ) oriented growth at different growth parameters and each orientation develops strain due to residual stress. The optical absorption indicates a direct type band gap for these films. The band gap of each ( hkl ) orientation varies linearly with its uniaxial strain. The three ( hkl ) orientations show band gap anisotropy (2.94–4.25 eV). The negative (for (101) and (111)) and positive (for (013)) pressure coefficients of band gap are attributed to the strain in Br–Br and Ba–Br bonds along [ hkl ] respectively. The average pressure coefficient of band gap of all three orientations found to be significantly smaller than that calculated by volumetric pressure dependence. [ABSTRACT FROM AUTHOR]

• Structural and optical properties of orthorhombic TlI films are investigated using DFT calculations and experiment. • Films show a perfect (0 4 0) oriented growth with strain without exception for any growth condition. • Hill's value of Young's modulus (16.72 GPa) and Poisson ratio (0.329) were calculated for strain to stress conversion. • Direct Band gap of films linearly correlate with their residual stress with pressure coefficient of band gap −1eV/GPa. • Stress free band gap of 2.92 eV from experiment tallies very well with calculated 2.88 eV from band structure. Perfectly (0 4 0) oriented Thallium iodide films grown by vacuum thermal evaporation were found to have strain and band gap uncorrelated with their film thicknesses. Band structure of orthorhombic TlI was calculated using Density functional Theory (DFT) with appropriate functional. Elastic constants were calculated for determining the residual stress from strain. Band gaps of films linearly correlate with their residual stress. Experimental stress free direct band gap 2.92 eV determined from band gap-residual stress correlation matches quite closely with calculated 2.88 eV. Pressure coefficient of band gap −1 eV/GPa was determined from the residual stress dependence of band gap. [ABSTRACT FROM AUTHOR]

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]

• Optical properties of monoclinic SbI3 are investigated using DFT calculations and experiment. • The calculated absorption spectra of six (hkl) planes show highly anisotropic nature. • 2.66 eV or 2.7 eV are possible indirect band gaps from band structure compared to measured 2.8 eV. • One exciton appears at 3.56 eV for (hkl) oriented film and two excitons at 2.95 eV and 3.30 eV for (1 3 0) • The experimental and theoretical optical properties match reasonably well. Structurally characterized antimony triiodide films grown by vacuum thermal evaporation exhibit anisotropic exciton formation at room temperature for different (hkl) oriented growth. Band structure of monoclinic SbI 3 was calculated using Density functional Theory with appropriate functional along with the absorption spectra of different (hkl) planes for comparing with the experimental results. The indirect band gap of 2.8 eV determined by measured absorption spectra matches closely with the calculated 2.66 eV. All (hkl) oriented films show one exciton at 3.56 eV which can be interpreted as direct type along D symmetry from the band structure. Similarly, the two excitons at 2.95 eV and 3.30 eV appearing for (1 3 0) oriented films can also be direct either at D or B symmetry. All three excitonic transitions are found to be from Iodine p states to Antimony p states. [ABSTRACT FROM AUTHOR]