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Single crystals (Ga 55 In 45 ) 2 S 300 and (Ga 54.59 In 44.66 Er 0.75 ) 2 S 300 possessing space group P6 1 were successfully grown and explored with respect to laser induced piezooptics. Their structural properties were studied by Raman spectroscopy and additionally, dependence of different gamma ray doses on the photoinduced piezo-optical responses were also explored. Structural parameters were evaluated using the Rietveld methods following the X-ray diffraction data. The chemical composition of the synthesized samples was determined by EDS analysis. We discussed the influence of Er 3+ -doping on the crystal structure and piezo-optical properties. It was established that these crystals behavior is very sensitive to γ−irradiation dose and therefore they are promising for applications as elastooptical radiation sensors. [ABSTRACT FROM AUTHOR]

In the present work, details of the crystal growth (Bridgeman method) and optical reflection spectroscopy for two single crystals (X = S, Te) were reported. Detailed ab-initio DFT calculations of the structural, electronic and optical properties of the crystals were performed for a deeper understanding of the experimentally obtained optical data. The special attention is paid to the electron charge density distribution, carrier mobility, optical reflectivity spectra and finally the anisotropy of the corresponding optical functions were studied. Were established a relations with carrier mobility, the optical anisotropy and electronic band structures for the titled crystals and compared with the optical reflectance spectra, covering the range of principal inter-band transitions. The origin of the calculated bands and effects of the anion substitution (Se by Te) on the crystal properties are studied. The role of screening effects is discussed by a comparison of the GGA and LDA approaches, including the electronic band dispersion and effective masses anisotropy. The possible changes of the inter-band transition are considered. The relation between the space charge density distribution and optical features is established. Finally was explained the origin of the observed discrepancies between the experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Single crystals of three oxide compounds containing stoichiometric Nd, doped with Yb 3+ ions, namely K 5 Nd(MoO 4 ) 4 (KNM), RbNd(WO 4 ) 2 (RNW), and NdAl 3 (BO 3 ) 4 (NAB) were grown from melts using Czochralski method or top seeded solution growth technique. Nd 3+ fluorescence characteristics were measured in dependence of Yb 3+ content and temperature. It was established that increasing Yb 3+ content results in a decrease of the Nd 3+ lifetime. However, the corresponding decay times values were quite different and varied from 9.5 μs for NAB up to 60 μs for KNM and 3.3 μs in RNW. Judd–Ofelt theory was applied to estimate the intrinsic lifetime of the 4 F 3/2 emitting level of Nd 3+ for all three crystals. The calculated lifetime values are much higher than the measured values. This effect is attributed to the strong concentration quenching of the Nd 3+ ions due to their high concentration in all three crystals. The possible mechanisms of the observed dependences are given. [ABSTRACT FROM AUTHOR]

A common feature of chalcogenide crystals is the presence of the chalcogen-chalcogen bonds, which result in very stable anion sub-structures (blocks) containing up to eight chalcogenide ions with the electric charge − 2 in units of the proton charge like systems [PS 4 ]3-, [SiS 4 ]4-, [GeS 4 ]4-, [GeSe 5 ]4-, [Ge 2 Se 6 ]6-. The size of anion blocks, their mutual arrangement and chemical bonds between them consequently determine the optical and detection properties. By modifying the chemical composition with subsequent use of the laser irradiation, it is possible to change crystal optoelectronic properties in a wide spectral range. In the work, we discuss the influence of the structural properties on the stability, electronic, optical and nonlinear-optical efficiency for the group of quaternary chalcogenide crystals with Ag(Pb)–Ga(In)–Si(Ge)–S(Se) composition, that have already found practical applications in IR optoelectronics and non-linear optics. The presented analysis of chemical composition-structure - nonlinear optical properties relationship can be useful for the creation of effective quaternary crystals for nonlinear optics application. • Influence of the structure on the nonlinear-optical efficiency for quaternary chalcogenide crystals is discussed. • The phonon subsystem significantly affects the value of second order optical susceptibility. • Quaternary chalcogenides are more effective NLO materials for use in the medium IR range than their triple counterparts. • With the increasing band gap width increase the efficiency of generating the second harmonic. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electronic band structure of pure and Yb-doped RbNd(WO4)2 crystals are obtained. [•] Ab initio calculations and spectroscopic ellipsometry measurements are used. [•] Dielectric function of the crystal in the range of 4–10eV is formed by WO4-groups. [•] Changes of dielectric function due to Yb doping and due to anisotropy are comparable. [ABSTRACT FROM AUTHOR]

The objective of this work is to explore the Ag ion concentration dependence on structural and dielectric characteristics of Na 2 O Sb 2 O 3 : Ag 2 O glass ceramics. The prepared glass ceramics were characterized by XRD, XPS, SEM, TEM, EDS and DSC techniques. These studies have revealed that the samples are composed of multiple crystal grains entrenched in the remnant amorphous phase. The IR and Raman spectroscopic studies indicated increasing degree of polymerization of the glass network with increase of Ag 2 O concentration up to 0.1 mol%. This is attributed to increasing concentration of tetrahedral Sb5+ ions that take part in the glass network forming. Optical absorption spectra have exhibited surface plasmon resonance (SPR) band in the wavelength region 400–450 nm. Quantitative studies on dielectric properties were performed over wide ranges of frequency and temperature and the variations of these properties with the concentration of Ag 2 O are discussed in the light of various polarization processes. Dipolar orientational effects exhibited by electric moduli spectra suggested multiple relaxation times for electric dipoles. The observed decrease of A.C. conductivity (that contains both ionic and polaronic components) with increase of Ag 2 O content up to 0.1 mol% is attributed to the increasing degree of polymerization of the glass network that hinders the migration of charge carriers. The polaronic conduction is understood due to exchange of polarons between Sb3+ ‒ Sb5+ and Ag0 Ag+ ions, while ionic conductivity is predicted due to transport of monovalent silver and Na+ ions. A changeover of polaronic to ionic conductivity seemed to take place at about 0.1 mol% Ag 2 O. Impedance plot for sodium antimonate glass crystallized with 0.1 mol% of Ag 2 O. Image 1 • Structural and dielectric properties of Na2O Sb2O3: Ag2O glass ceramics investigated. • Structural studies indicated samples contain Sb3+, Sb5+, Ag+, Ag0 crystal phases. • Samples with >0.1 Ag mol% exhibit larger ionic conductivity. • Polaronic component of a.c. conductivity is prevailed up to 0.1 mol% of Ag 2 O. [ABSTRACT FROM AUTHOR]

Abstract In the present work, we investigate, in detail, the phase diagrams of the TlGaSe 2 –Zn(Cd,Hg)Se systems, which are quasi-binary and eutectic type. The solid phase solubility on the basis of components did not exceed 5 mol% at 670 K. The crystals of TlGaSe 2 : Zn+2(Cd+2, Hg+2)) solid solutions were prepared by Bridgman-Stokbarger method. It was established that the doping of Zn+2, Cd+2, Hg+2 leads to a slight decrease in the values of both the direct and indirect band gap energies with respect to the that in undoped TlGaSe 2 crystal. The temperature dependence of the band gap values for all the synthesized compounds is crucial for semiconductor applications. Also, the dominant mechanisms are proposed that contribute to the fundamental absorption edge tailing. Graphical abstract Image 1 Highlights • High quality TlGaSe 2 crystals, doped by Zn+2 or Cd+2 or Hg+2 crystals has been successfully growth for first time. • Single crystals were grown using a horizontal version of Bridgman -Stokbarger method. • Doping decrease of both the direct and indirect band gap energy with respect to the undoped TlGaSe 2 crystal. • Phase diagrams of the TlGaSe 2 –Zn(Cd)Se systems were investigated by DTA, XRD and microstructure analysis. [ABSTRACT FROM AUTHOR]

New quaternary sulfide PbGa 2 GeS 6 crystal was synthesized from co-melting high-purity elements The studies of second harmonic generation and the third harmonic generation for new quaternary sulfide PbGa 2 GeS 6 crystal have shown that its nonlinear optical response is higher with respect to other similar compounds. The band structure analysis performed by X-ray spectroscopy methods and first principles DFT band structure calculations indicate that the main contributions of the S 3p states are located at the top of valence band, while those of the Ga 4p states give contribution to the central and upper portions of the valence band of the PbGa 2 GeS 6 compound. The calculations reveal that the band gap E g  = 2.445 eV is indirect and is formed between the valence Γ-point and the conduction X-point of Brillouin zone. The theoretically evaluated band gap energy is close to the experimental value, namely E g  = 2.37 eV at 300 K The present results allow recommending PbGa 2 GeS 6 for nonlinear optical application in the near IR spectral range. At the same time, the crystal possesses a good transparency in the mid-IR spectral range. [ABSTRACT FROM AUTHOR]

Article reports design and synthesis, technology, crystal structure determination and results of photoinduced nonlinear optical investigations of novel TlInGe 2 S 6 crystals. We have discovered TlInGe 2 S 6 as a new type of laser induced nonlinear optical materials. Following the performed measurements we can use the titled crystals for laser operated coherent wavelength transformations. It was shown, that thin, photoinduced nanolayers formed by laser energies above the energy gap as well a near the phonon resonances possess promising nonlinear optical properties. Different types of cw lasers with the same powers of the photoinduced beams were used: SHG of the Nd:YAG laser (532 nm), fundamental Nd:YAG laser (1064 nm), and IR CO 2 laser with wavelength of 9400 nm. The crystal structure of novel quaternary thallium indium germanium sulphide TlInGe 2 S 6 determined by X-ray powder method possesses trigonal space group R 3. The as-derived TlInGe 2 S 6 crystalline alloy was probed employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. Particularly, for the TlInGe 2 S 6 alloy surface, both pristine and 3.0 keV Ar + ion-irradiated, we have monitored the XPS valence-band and core-level spectra. These measurements indicate that the TlInGe 2 S 6 surface is rather stable with respect to Ar + ion-irradiation, which does not induce significantly near the surface layers sub-stoichiometry. Matching on a common energy scale of the XPS valence-band spectrum and the XES S Kβ 1,3 and Ge Kβ 2 bands indicates that main contributions of the S 3p and Ge 4p states are located in the upper and central portions of the valence band of TlInGe 2 S 6 , respectively, with significant contributions of these states in other valence-band parts as well. [ABSTRACT FROM AUTHOR]

A nearly centimeter-size Tl 2 HgSnSe 4 crystal was successfully derived by Bridgman-Stockbarger growth technique and its electronic and optical properties are investigated experimentally and theoretically. The present XPS experiments imply very little hygroscopic behavior of the Tl 2 HgSnSe 4 crystal surface, a characteristic property to be very important for practical use of this crystal in devices working at ambient atmospheric conditions. The experimentally determined energy band gap, 1.26 eV, and high values of the photocurrent spectral dependence confirm that Tl 2 HgSnSe 4 crystal is a high-resistance photosensitive semiconductor possessing the p-type conductivity. The finest agreement with the experiment is detected when the theoretical calculation of the electronic structure of Tl 2 HgSnSe 4 is carried out using modified Becke-Johnson functional for the exchange-correlation potential and involving the Hubbard amendment parameter U and the spin-orbit coupling effect. The present experimental and theoretical data suggest good perspective of application of Tl 2 HgSnSe 4 in optoelectronics and as a suitable material of solar photovoltaics. [Display omitted] • Tl 2 HgSnSe 4 crystal was grown for the first time by Bridgman-Stockbarger method. • Tl 2 HgSnSe 4 is a p-type high-resistance photosensitive semiconductor with E g = 1.26 eV. • Electronic structure of the Tl 2 HgSnSe 4 crystal was investigated by XPS and XES. • Band-structure calculations within the mBJ+U+SO model are in agreement with experiments. • Principal optical properties of Tl2HgSnSe4 are explored in detail. [ABSTRACT FROM AUTHOR]

We show the opportunity for tuning of the spectral position of the Mn4+ red emission in the series of double perovskites, Ba 2 LaNbO 6 :Mn4+, Ba 2 La(Nb 0.8 ,Zr 0.1 ,W 0.1)O 6 :Mn4+, and Ba 2 La(Zr 0.5 ,W 0.5)O 6 :Mn4+ with increasing chemically induced symmetry disturbance. Such a disorder appeared attractive to engineering phosphors for pressure sensors or horticultural applications, for instance. The goal of the present research, not yet systematically addressed in the literature, was to unveil the correlation between chemically induced controlled crystal lattice distortion and the luminescence of Mn4+. For this purpose, the luminescence of these phosphors was methodically investigated at different pressures and temperatures. A pressure-induced redshift of photoluminescent lines with the rate of − 4 cm−1/kbar was found within the 0–230 kbar range, and the emission peak moved from 685 to 740 nm then. Furthermore, the cationic disorder allowed tuning of the Mn4+ luminescence making it useful for horticultural applications with a better fit between the emission wavelength and the strong chlorophyll absorption in the deep red part of the spectrum. The Mn4+ energy levels were computationally determined using the exchange charge model of the crystal-field theory which allowed for a deeper understanding of the experimental results. We found a correlation between the introduced disorder of the cationic subsystem and the energy of the Mn4+ emitting 2E g level (R-line) as well as its intensity. This research brought a deeper understanding of the Mn4+-activated phosphors and, in turn, provides tips for a prudent search of materials for advanced practical uses. [Display omitted] • The Ba 2 La(Nb 1–2x Zr x W x)O 6 :Mn (x = 0;x = 0.1;x = 0.5) isostructural phosphors are reported. • The influence of pressure and temperature on the luminescence of Mn4+ is presented. • Effects of chemically induced partial cation substitution are investigated. • Theoretical studies support the understanding of the experimental dependencies. • The findings provide tips for a deliberate design of phosphors for advanced uses. [ABSTRACT FROM AUTHOR]

This investigation is mainly devoted to the studies on enrichment of green emission of Ho 3+ ions in PbO SiO 2 glasses containing 1.0 mol% of Ho 2 O 3 by co-doping with different concentrations of Bi 2 O 3 (0–9.0 mol%). The optical absorption spectra, photoluminescence spectra, photoluminescence decay, IR and Raman spectral studies on the above mentioned glasses have been performed as a function of Bi 2 O 3 concentration. The emission spectra of Bi 2 O 3 free glasses exhibited green and red emissions due to 5 S 2 + 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ ions, respectively, when excited at 450 nm. The spectra also exhibited NIR emission due to the 5 I 7 → 5 I 8 transition at 2.0 μm. The intensity of green emission is found to be significantly enhanced (nearly three times) when the glasses are mixed with 5.0 mol% of Bi 2 O 3 . The reason for this enhancement has been identified as being due to the energy transfer from Bi 3+ to Ho 3+ ions. The predominant participation of Bi 3+ ions in modifying positions and due to the de-clustering of Ho 3+ ions are found to be the other reasons. The overall enhancement of emission has further been explained with the help of rate equations. The quenching of luminescence emission observed in the glasses containing more than 5.0 mol% of Bi 2 O 3 is attributed to the reason that in these glasses the Bi 3+ ions largely participate in the network forming positions and increase the phonon losses. These arguments have been quantitatively explained with the help of IR and Raman spectral studies. [ABSTRACT FROM AUTHOR]

Exploring better Gamma, X-Ray and IR-Mid-R detectors, adequately sensitive to ambient temperatures and environmental conditions, is highly desirable. Therefore, following this path, we present detecting opportunities, based on data of experimental and theoretical investigation of the electronic and optical properties, photocurrent behavior at different bias voltages as well as the reflection for the He-Cd cw laser after irradiation by three different IR laser wavelengths, for recently grown TlPb 2 BrI 4 single crystal with strong anisotropic, two-dimensional (2D) layered structure. The X-ray photoelectron spectroscopy brings data on binding energy values of core levels of TlPb 2 BrI 4 for both as-grown and Ar+-ion-treated crystal surfaces as well as for elucidation of the energy distribution of the valence electronic states. In opposite to well-known IR-detector materials, TlPb 2 BrI 4 crystal surface shows high chemical stability concerning Ar+-ion bombardment. Further, we carry out ab initio band-structure calculations to gain curves of total and partial densities of states and to elucidate the principal optical constants of TlPb 2 BrI 4. The present studies indicate that, in spite of the fact that the TlPb 2 BrI 4 crystal contains two very hazardous/toxic chemical elements, thallium and lead; however, it is chemically stable and reveals very low hygroscopic behavior when being exposed to environmental conditions. [Display omitted] • Measurements of the time-resolved photocurrent are performed for TlPb 2 BrI 4 crystal. • Explanation of conversion rate of TlPb 2 BrI 4 crystal in the framework of the layered 2D structure is made. • IR photoinduced changes in reflectivity geometry of TlPb 2 BrI 4 are explored. • Crystal structure of novel layered TlPb 2 BrI 4 compound is refined. • Electronic structure and optical properties of TlPb 2 BrI 4 crystal are studied in detail. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL) studies on PbO–Al 2 O 3 –SiO 2 :Nd 3+ glasses mixed with varying concentrations of Al 2 O 3 exposed to γ-rays of dose in the range 0–5.0 kGy were carried out. The TL emission exhibited a dosimetric peak at about 185 °C. The TL output under the glow peak increased with increasing Al 2 O 3 and also with the γ-ray dose. The mechanisms responsible for TL emission and enhancement of TL output with increase in the concentration of Al 2 O 3 were quantitatively discussed in terms of induced structural defects in the vicinity of Nd 3+ ions due to interaction of γ-rays with the glass network in the scenario of varying concentration of Al 2 O 3 . The dose response of these glass samples exhibited linear behavior in the medium dose range viz., 1.0–3.0 kGy. Finally, it is concluded that the glass containing the highest concentration of Al 2 O 3 exhibits high TL output and such glasses are useful for dosimetry in the range 1.0–3.0 kGy and hence these glasses may be useful for dosimetry in such high range of doses required for commercial radiation processing of perishable food commodities to extend their shelf-lives. [ABSTRACT FROM AUTHOR]

Highlights: [•] Emission features of Dy3+ ion were studied as a function of Al2O3 concentration in lead silicate glasses. [•] The emission spectra exhibited bands due to 4F9/2 → 6H15/2(B),6H13/2 (Y), 6H11/2 and 6H9/2 transitions. [•] The Y/B integral intensity ratio is found to decrease with increase in the concentration of Al2O3. [•] The decrease Y/B ratio is explained interms of structural modifications in the vicinity of the Dy3+ ion. [Copyright &y& Elsevier]

Abstract: PbO–Sb2O3–B2O3 glasses mixed with different content of Pr2O3 (ranging from 0 to 0.6mol%) were crystallized. The samples were characterized by X-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetric (DSC) techniques. The TEM studies indicated that the samples contain well defined and randomly distributed nanoclusters possessing the sizes within ∼30–40nm. The XRD spectra have exhibited diffraction peaks due to presence of Pb5Sb2O8, Pb3(SbO4)2, PbB4O7, β-PrSbO4, Pr3SbO7, Pr3Sb5O12 crystalline phases. From these spectra, it was identified that the antimony ions co-exist in Sb5+ state with Sb3+ state in the titled glass ceramic samples. The photo-induced birefringence (changes in refractive indices) caused by simultaneous exposure of the sample with the doubled frequency coherent laser beam (1.54μm and 0.77μm) was monitored by polarized probing beam of varying wavelength in the range of 750–1250nm. The induced birefringence exhibited a maximum at about 1000nm, a wavelength corresponding to 3H4 → 1G4 optical excitation transition of Pr3+ ion. We have established a correlation between the intensity of this transition and the birefringence dispersion. Principal role of the photo-occupation of this transition is identified. The variations of photo-induced birefringence with increase in the content of Pr2O3 is explained due to the increasing degree of disorder and increasing concentration of deformed PrO8 structural units in the glass ceramic. Further analysis of these results coupled with the data on IR and Raman spectral studies, has indicated that PbO–Sb2O3–B2O3 glasses crystallized with 0.6mol% of Pr2O3 exhibit maximal birefringence effects. [Copyright &y& Elsevier]

Abstract: The absorption spectra of (NH2(C2H5)2)2CuCl4 (DEACC) single crystals and nanocrystals (NC) incorporated into the polymethyl methacrylate (PMMA) polymer matrices were investigated both experimentally and theoretically. It was established that the crystal field spectra of Cu2+ ion detect clearly the quantum size effects. The observed spectra were analyzed using first principle crystal field quantum chemical calculations. It was shown that incorporation of NCs into the polymer matrix allows to identify the charge-transfer (CT) bands in the spectra of DEACC crystals. [Copyright &y& Elsevier]

Abstract: NdAl3(BO3)4 single crystals with different concentrations of Yb3+ were grown using the top seeded solution growth method. The absorption spectra of the grown samples were recorded at room temperature and analyzed using the standard Judd–Ofelt theory. Influence of Yb3+ concentration on the Nd3+ absorption properties was studied. Variation of the Nd3+ oscillator strengths with changing Yb3+ concentration suggests significant role of the Yb–Nd energy transfer in the formation of the absorption spectra. Following the absorption spectra we illuminated the investigated crystals at 532nm absorption line to observe the changes of the two-photon absorption (TPA). We observed substantial increase of the TPA with the increased power of the illuminating laser which was proportional to the Yb content. [Copyright &y& Elsevier]

Abstract: PbO–Sb2O3–B2O3 glasses mixed with different concentrations of TiO2 (ranging from 0 to 1.5mol.%) were synthesized. The samples are characterized by X-ray diffraction, scanning electron microscopy and DSC techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra, magnetic susceptibility, photo-induced birefringence (PIB) and dielectric properties (constant ɛ′, loss tan δ, a.c. conductivity σ ac over a wide range of frequency and temperature) of these glass–ceramics have been explored. The analysis of these results indicated that Ti ion surrounding ligands play principal role in the observed PIB and the sample crystallized with 0.8mol.% of TiO2 is the most suitable for the applications in non-linear optical devices. [Copyright &y& Elsevier]

Abstract: A complex spectroscopic study of Ca4GdO(BO3)3 (GdCOB) doped with Pr3+ has been performed experimentally and theoretically using the ab initio configuration interaction (CI) calculation method. This approach is based on the numerical discrete-variational Dirac-Slater cluster calculations and numerical solution of the Dirac equation using the local density approximation. All relativistic effects are considered automatically by virtue of the relativistic Hamiltonian. The principal novelty of the approach is that during the calculations the molecular orbitals (MO) consisting of the atomic wave functions of the central ion (in this case, Pr3+) and its nearest ligands (O2−) are used. The principal advantage of the method consists in ab initio approach not requiring the fitting parameters like in the widely used crystal field approach or FLAPW requiring the muffin tin orbitals. Such a complete basis set allows not only to evaluate the main energy terms, but also to analyze the covalent charge transfer effects and to evaluate the energy separations between different MO groups. Using the GdCOB:Pr single crystals as good probes to check the introduced theoretical model, we report the calculations of the complete energy terms (including unoccupied excited MO) for the principal [PrO6]9− cluster. Theoretical simulations are verified by comparison with both the ground and excited state absorption. A particular interest presents estimations of the crystal field splitting of the localized Pr3+ 5d orbitals (10 Dq) (about 20,800cm−1) and energy separations between the 2p (O2−)–4f (Pr3+), 2p (O2−)–5d (Pr3+), and 2p (O2−)–6s (Pr3+) MO (13,300, 40,050, and 78,900cm−1, respectively). These values are in sufficient agreement with performed excited state absorption experimental data and available ground state absorption data including the low temperatures study at 4.2K. Several discrepancies between the calculated and measured intensities of the optical transitions can be explained by contribution of electron–phonon coupling and sample''s imperfections. In addition to the first principles calculations, crystal field theory was used to calculate the Pr3+ energy levels; a set of crystal field parameters for Pr3+ ion in GdCOB crystal is suggested. [Copyright &y& Elsevier]

Abstract: Experimental measurements of linear electro-optical coefficients are reported for Bi x La y Sc z (BO3)4 (x + y + z =4) (BLSB) nanocrystallites incorporated into polymer matrices of different polarizabilities. The nanochromophores in the matrices were oriented by external dc-electric field during spin coating. The measurements were performed under illumination of CW semiconducting GaAlAs laser emitting at 1040nm. We have achieved the maximal values of the Pockels coefficients equal to 3.5pm/V for the BLSB nanocrystallites incorporated into the polycarbonate matrices. The optimal sizes of nanocrystallites were below 20nm and their content was equal to about 7.5% (in weight. units). We have eliminated a contribution to the Pockels effect due to the piezo-optical coefficients as well as due to other bothering factors. The temperature influence is very low (due to low ionic contribution), and do not exceed 6%, which is related to low contribution of electron–phonon interaction to the Pockels effect. So these alloys may be proposed as promising materials for high power laser electro-optic modulators. [Copyright &y& Elsevier]

Successful synthesis by vertical solidification (Bridgman - Stockbarger) technique is reported for a centimetre size noncentrosymmetric TlSbP 2 Se 6 crystal (for the first time) with excellent transparency at 0.75–10 μm that is very useful for its practical application. The high homogeneity and stoichiometric composition have been confirmed by SEM-EDX. Next we determined the crystal structure, electronic properties by use of both experimental and theoretical methods. The layered structure of the crystal provides strong anisotropy of physical properties. Special attention was placed for an explanation of the source of the layer architecture and its effect on the strong anisotropy of properties. In particular, employing the XPS method, we have measured for the TlSbP 2 Se 6 crystal the binding energies of core-level electrons as well as energy distribution of the valence electrons for both pristine and treated with Ar+ ions surfaces and shown that the TlSbP 2 Se 6 crystal surface is highly hygroscopic. For interpretation and explanation of the measured XPS valence band spectrum, we examined different approaches for exchange correlation (XC) potential with a density functional theory (DFT) framework and found that the best agreement of the shapes of the XPS spectrum and the curve of total density of states is derived when the band structure calculations were made employing for XC potential modified Becke-Johnson (mBJ) functional in the form of Tran and Blaha. Based on the results of XPS measurements and calculations, we explained the contributions of individual ions to the band structure and convincingly demonstrated that ionic components of the chemical Sb–Se (P–Se) bonds in the TlSbP 2 Se 6 crystal are similar to those of its silver-bearing counterpart AgSbP 2 Se 6. The present DFT calculations within TB-mBJ + U + SO approach reveal that the TlSbP 2 Se 6 compound is a non-direct semiconductor with E g = 1.765 eV confirmed by UV-VIS measurements (1.75 eV). The main optical constants are explored in detail for TlSbP 2 Se 6 , as based on TB-mBJ + U + SO calculations. Finally, the result of the XPS investigations of the crystal surface after treatment with Ar+ ions supported by the calculations of the structure indicates its high chemical and mechanical resistance, which, despite the dangerous element contained in the composition, indicates its safe use in optoelectronic devices. • High quality TlSbP 2 S 6 single crystal with transparency at 0.75–10 μm has been grown for first time. • The appearance of the layered architecture of structure is explained. • TlSbP 2 Se 6 is a promising IR NLO material with band gap of 1.75 eV. • Electronic properties were probed employing the XPS and XES methods. • Excellent agreement with DFT approximation (TB-mBJ + U + SO) was achieved. [ABSTRACT FROM AUTHOR]

The theoretical studies of Ag 2 SiS 3 chalcogenide crystal properties are performed using the first-principles calculations within density functional theory. The pseudopotential method with the plane waves basis and generalized gradient approximation for exchange-correlation interaction were used for calculations. The peculiarities of the Ag 2 SiS 3 crystal structure are analyzed taking into account the second coordination sphere environment. The bandgap of the crystal is established to be of the with the numerical value of E g = 1.42 eV. The dielectric function dispersion for the studied crystal is calculated, from which the refractive indices dispersion for Ag 2 SiS 3 is obtained. Both dielectric function and refractive indices reveal relatively low anisotropy level. All elastic parameters of the titled crystal are calculated. The elastic properties exhibit high anisotropy, which was visualized by plotting spatial distributions of the directional dependence of the Young's modulus E. • Detailed ab initio calculations for Ag 2 SiS 3 crystal are performed. • Anisotropy of optical and elastic properties of Ag 2 SiS 3 crystal was modeled. • Remarkably large difference between Young moduli along principal axes of crystal is detected. [ABSTRACT FROM AUTHOR]