Infrared vibrational Modes in Tl3SbS3, Tl3AsS3, and Tl3AsSe3 crystals

Reflectivity spectra of Tl₃SbS₃, Tl₃AsS₃, and Tl₃AsSe₃ crystals have been investigated in the wave number range 50–600 cm⁻¹ for the polarizations E∥c and E⟂c. The fundamental phonon parameters, the limiting dielectric constants ϵ_∞ and ϵ_S and the reflectivity spectra contours have been calculated by using classical dispersion relations for both E∥c and E⟂c configurations. The Szigeti effective charges and the relative ion charges of As, Tl, Sb, Se, S anions and cations have been calculated in dependence on the incident light polarization.     

Preparation and fundamental physical properties of Sn2SbS2I3 and Pb2SbS2I3 compounds

The oriented ingots of isostructural compounds Sn₂SbS₂I₃ and Pb₂SbS₂I₃ were prepared using a modified Bridgman method. The lattice parameters of the prepared orthorhombic compounds have been determined by a X-ray powder diffraction analysis. From the spectral response of the photoconductivity the following values for the forbidden zone of the prepared sulfides-iodides were found: E_g(Sn₂SbS₂I₃) 1.5 eV, E_g(Pb₂SbS₂I₃) = 2.0 eV.     

Temperature‐tuned band gap energy and oscillator parameters of Tl2InGaSe4 semiconducting layered single crystals

The optical properties of Tl₂InGaSe₄ layered single crystals have been studied through the transmission and reflection measurements in the wavelength range of 500‐1100 nm. The analysis of room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.86 and 2.05 eV, respectively. Transmission measurements carried out in the temperature range of 10‐300 K revealed that the rate of change of the indirect band gap with temperature is γ = – 4.4 × 10^‐4 eV/K. The absolute zero value of the band gap energy was obtained as E_gi(0) = 1.95 eV. The dispersion of the refractive index is discussed in terms of the single oscillator model. The refractive index dispersion parameters: oscillator wavelength and strength were found to be 2.53 × 10^–7 m and 9.64 × 10¹³ m^–2, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Infrared Lattice Vibrations of TI3AsS4

Infrared reflectivity spectra of TI₃AsS₄ single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm⁻¹ for the polarization directions E ‖ c and E ‖ a. An analysis of the spectra with the Kramers-Kronig method reveals 10 infrared active modes for each of the polarization directions. On the basis of theoretical estimates the modes due to TI-S and As–S bond vibrations are identified.     

Stereochemistry of 1,2-oxaphospholanes. Part X. Synthesis,X-ray structure and NMR spectroscopy of (2S*,3R*,5R*)-2-methoxy-3,5-dimethyl-2-oxo-1,2-oxaphospholan-3-ol

The title compound (4a) was synthesized from a phosphite compound obtained from 4-hydroxy-2-pentanone and dimethylphosphorochloridite, after addition of an equivalent of water. Thecis-configuration of the P=O and C3-OH groups was established based on³¹P NMR chemical shifts. In chloroform, as well as in benzene solution, the most favorable conformations of the title compound are ₄ ⁵ T,⁴ E, and ₄ ⁵ T. The crystal and molecular structure of4a has been determined by single-crystal X-ray diffraction data, and refined toR=0.056. The five-membered ring has an envelope⁴ E (C₅) conformation, with the asymmetry parameter C ₅(4)=3.5°. Both the C5-CH₃ and the C3-CH₃ groups are equatorial. In the solid state, the molecules form dimers with hydrogen bonding between the hydroxyl groups and the phosphoryl oxygen atom of an adjacent molecule. A quantitative comparison of the structure of 4a with the structure of the related 2-mcthoxy-3,5,5-trimethyl-2-oxo-1,2-oxaphosphospholan-3-ol is given.     

Mikrohärteuntersuchungen an Einkristallen der Verbindungen Tl3BX4, (B = V,Nb, Ta; X=S,Se)

Vickers microhardness measurements were performed on single crystals of compounds Tl₃BX₄ (B = V, Nb, Ta; X = S, Se). The anisotropy of the hardness on the (111)-plane was beyond the standard deviation. Besides the load-dependent Vickers hardness HV, the corrected, load-independent hardness HV_c was determined. Tl₃VS₄ showed the highest value of hardness (HV = 66 kp/mm² at 15 p load), the othe compounds differ only slightly in hardness.     

Influence of thermoannealing on crystallinity and optical properties of Sb2S3 thin films

Sb₂S₃ thin films are obtained by evaporating of Sb₂S₃ powder onto glass substrates maintained at room temperature under pressure of 2×10^‐5 torr. The composition of the thin films was determined by energy dispersive analysis of X‐ray (EDAX). The effect of thermal annealing in vacuum on the structural properties was studied using X‐ray diffraction (XRD) technique and scanning electron microscopy (SEM). The as‐deposition films were amorphous, while the annealed films have an orthorhombic polycrystalline structure. The optical constants of as‐deposited and annealed Sb₂S₃ thin films were obtained from the analysis of the experimental recorded transmission spectral data over the wavelength range 400‐1400 nm. The transmittance analysis allowed the determination of refractive index as function of wavelength. It was found that the refractive dispersion data obeyed the single oscillator model, from which the dispersion parameters (oscillator energy, E₀, dispersion energy, E_d) were determined. The static refractive index n(0), static dielectric constant, ε_∞, and optical band gap energy, E_g, were also calculated using the values of dispersion parameters. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Specific features of the optical spectra in Tl2In2S3Se layered single crystals

The optical properties of Tl₂In₂S₃Se layered single crystals have been studied by means of transmission and reflection measurements in the wavelength range of 450‐1100 nm. The analysis of the absorption data revealed the presence of both optical indirect and direct transitions with energy band gaps of 2.16 and 2.42 eV, respectively. The observed coexistence of indirect and direct energy band gaps is related to the anisotropy of the Tl‐containing layered crystals. The dispersion of the refractive index is discussed in terms of the Wemple‐DiDomenico single‐effective‐oscillator model. The refractive index dispersion parameters: oscillator energy, dispersion energy, oscillator strength and zero‐frequency refractive index were found to be 4.78 eV, 43.58 eV, 13.18 × 10¹³ m^–2 and 3.18, respectively. From X‐ray powder diffraction study, the parameters of monoclinic unit cell were determined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

NMR and infrared study of cation motion in vitreous and polycrystalline TlPO3

The activation energy for Tl⁺ conduction in TlPO₃ glass is obtained from analysis of temperature-dependent motional narrowing for Tl²⁰⁵ NMR spectra and determinations of the localized far infrared (FIR) vibrational frequency for Tl⁺. Use is made of the phenomenological equation of Hendrickson and Bray to analyze the NMR data, yielding E_a = 1.19 eV; the measured FIR Tl⁺ vibrational frequency of 80 cm^?1 yields E_a = 1.09 eV. No significant ionic conduction is observed in polycrystalline TlPO₃. Differential scanning calorimeter measurements yield a glass transition temperature T_g of 96°C and the onset of crystallization temperature of 132°C. Measurements of the Tl²⁰⁵ chemical shift interaction as a function of frequency indicate that (1) the Tl⁺ sites in both polycrystalline and glassy TlPO₃ are ionic, the sites in the polycrystal being slightly more ionic than in the glass; (2) the chemical shift interaction is anisotropic in the glass and isotropic in the polycrystal; and (3) distributions in the values of the principal components of the chemical shift tensor exist in the glass, corresponding to a variety of TlO bond lengths and bond strengths.     

Infrared Lattice Vibrations of CdGa2Te4

Infrared reflectivity spectra of CdGa₂Te₄ crystals are measured at room temperature in the wavenumber range from 180 to 600 cm⁻¹ for the polarization directions E ⊥ c and E ‖ [111]. The frequencies of two E modes and two B modes are derived from the spectra. The frequencies of the modes with highest energy compare well with those of the corresponding modes in CuGaTe₂ and AgGaTe₂ which confirms the sphalerite-like nature of these modes.     

Synthesis,crystal growth and characterization of Tl3BX4-compounds (B = V,Nb, Ta; X = S,Se)

Single crystals of Tl₃BX₄-compounds (B = V, Nb, Ta; X = S, Se) were grown by the Bridgman-Stockbarger technique. The compounds were synthesized from the high-purity elements. The melting points were determined by differential thermal analysis. Tl₃VS₄, Tl₃TaS₄ and Tl₃TaSe₄ yielded single crystals up to 10 cm³. The other compounds show single crystalline pieces up to 1 cm³. Infrared photographs and electron microprobe analyses revealed inclusions of TlS in the sulfur compounds, in Tl₃VSe₄ and Tl₃NbSe₄ inclusions of TlSe and in Tl₃TaSe₄ small amounts of Ta.     

Thermoelectric properties of Tl‐doped Bi2Se3 single crystals

The single crystals of the ternary system based on Bi_2‐xTl_xSe₃ (nominaly x = 0.0‐0.1) were prepared using the Bridgman technique. Samples with varying content of Tl were characterized by the measurement of lattice parameters, electrical conductivity σ_⊥c , Hall coefficient R_H (B∥c), and Seebeck coefficient S (ΔT ⊥c). The measurements indicate that by incorporating Tl in Bi₂Se₃ one lowers the concentration of free electrons and enhances their mobility. This effect is explained in terms of the point defects in the crystal lattice – formation of substitutional defects thallium on the site of bismuth Tl_Bi and the decrease of concentration of selenium vacancies V_Se⁺². We also discuss the temperature dependence of the power factor σS² of the samples. Upon the thallium doping we observe a significant increase of the power factor compare to the parental Bi₂Se₃. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The superposition of the lattice radiation and reflectivity spectra of MoO3 and PbMoO4 crystals

The Raman scattering of MoO₃ at 300 and 77 K and the infrared reflectivity spectra of MoO₃ at 300 K have been investigated in different scattering geometries. The Raman spectra of PbMoO₄ crystals at 77 K have been investigated also. The reflectivity spectra of MoO₃ crystals were calculated for E ∥ c and E ∥ a. The phonon parameters and the effective ionic charges of anions and cations for MoO₃ and PbMoO₄ crystals are determined. The diagrams of the splitting of the vibrational levels by the Davydov resonance and by the factor group interactions have been determined. It is shown that the lattice radiation of crystals which have a number of vibrational oscillators (MoO₃, PbMoO₄) begins at low energy vibrational modes and at low values of the damping parameters.     

Synthesis,Crystal Growth,Structural and Physical Properties of bis(thallium) bis(nitrilotriacetato) zirconate dihydrate,Tl2Zr(N[CH2COO]3)2 · 2H2O

Single crystals of Tl₂Zr(N[CH₂COO]₃)₂ · 2H₂O having optical quality and dimensions up to 30 × 25 × 12 mm have been grown from aqueous solutions by controlled lowering of temperature. The raw material was synthesized as the first fraction of crystallization during evaporation of an aqueous solution of (CH₃NH₃)₂Zr(N[CH₂COO]₃)₂ · 2H₂O and TlNH₂SO₃. A crystal structure analysis revealed an isotypy to the K₂Zr(N[CH₂COO]₃)₂ · 2H₂O family, space group Ccc2, a₁ = 14.780(2)Å, a₂ = 14.933(2)Å, a₃ = 8.901(1)Å, Z = 4, ρ_calc. = 3.145 gcm^‐3. Thermal stability, thermal expansion and pyroelectric, dielectric, piezoelectric, elastic and thermoelastic properties have been determined. All properties are closely related to those of Rb₂Zr(N[CH₂COO]₃)₂ · 2H₂O.     

Refractive index dispersion of spinel Zn2TiO4 single crystal

The transmittance and absorption spectra of a high‐quality Zn₂TiO₄ single crystal have been measured along the a‐axes at room‐temperature in the range of 200‐1000 nm. The wavelength dependent refractive index, extinction coefficient, real and imaginary parts of the complex dielectric constant of the Zn₂TiO₄ crystal have been derived from the measured T and α spectra. By fitting the refractive index spectrum, the Sellmeier dispersion equation of the Zn₂TiO₄ crystal has been obtained. The validity of Cauchy‐Sellmeier equation has been evaluated in the energy range of 2.90–3.20 eV representing the Urbach tail. Applying the single‐effective oscillator model, the dispersion energy E_d and the oscillator energy E₀ have been determined as 18.76 and 5.05 eV, respectively. The obtained dispersion energy E_d takes on ionic crystal value. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Molecular structure of AlH3[N(CH2CH2)3CH]2

Reaction of AlH₃[N(CH₂CH₂)₃CH] with hexamethyltrisiloxane, (OSiMe₂)₃, gives rise to the bis-quinuclidine complex AlH₃[N(CH₂CH₂)₃CH]₂, which has been characterized by ¹H and ¹³C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH₃[N(CH₂CH₂)₃CH]₂ consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) ų, and Z = 4.     

Crystal Structure of a New Quinternary Oxide: NaTl<Subscript>3</Subscript>Cu<Subscript>4</Subscript>Te<Subscript>2</Subscript>O<Subscript>12</Subscript>

Abstract  

A new quinternary oxide, NaTl₃Cu₄Te₂O₁₂, has been synthesized and characterized by single crystal X-ray diffraction. The reported material was synthesized by hydrothermal techniques using TlNO₃, CuO, TeO₂, and NaOH as reagents. The material exhibits a two-dimensional layered structure consisting of edge-shared CuO₆ and TeO₆ polyhedra separated by Na⁺ and Tl⁺ cations. NaTl₃Cu₄Te₂O₁₂ crystallizes in space group C2/m with a = 12.9800(17) ?, b = 9.3455(12) ?, c = 5.2335(7) ?, β = 104.276(2)°, V = 615.24(14) ?³, and Z = 2.     

Variation of optical basicity with probe ion,for Cs2O + B2O3 and Li2O + B2O3 glasses

Optical basicities (Γ) for Cs₂O + B₂O₃ and Li₂O + B₂O₃ glasses have been measured as a function of glass composition, using Tl⁺, Pb²⁺ and Bi³⁺ probe ions. The three probe ions register different values of Γ for glasses of given composition (and also for pure B₂O₃ glass and water). The divergence decreases as the alkali metal ion size decreases.For the Li₂O + B₂O₃ glasses, ideal (calculated) optical basicities agree within experimental precision with experimental values registered by Pb²⁺ (Γ_Pb²⁺) up to about 15 mol% Li₂O. For higher Li₂O contents, and for the Cs₂O + B₂O₃ glasses, ideal optical basicities agree less well with Γ_Pb²⁺, but show similar trends with composition to those shown by Γ_Pb²⁺.     

Spectra and structure of organophosphorus compounds,XVIII: Infrared and Raman spectra of [(CH3)2PS]2, [(CD3)2PS]2, and [(CH3CH2)2PS]2 in the solid state

The infrared (80–3500 cm^–1) and Raman (10–3500 cm^–1) spectra of solid [(CH₃)₂PS]₂, [(CD₃)₂PS]₂, and [(CH₃CH₂)₂PS]₂ have been recorded. A complete vibrational assignment is proposed for tetramethyldiphosphine disulfide on the basis ofC _2h molecular symmetry. The observed intermolecular vibrations indicate little factor group effects, and no frequency differences were observed for the normal modes of the two different molecules which exist in the crystal as reported from the x-ray study. Most of the observed bands in the spectrum of tetraethyldiphosphine disulfide have been assigned. At least two of the three optical librational modes were observed in the Raman effect.     

Synthesis,properties, and structure of 1,3-dimethyl-2(3H)-imidazolethione hydrogen bromide

The compound dmit·HBr (dmit=1,3-dimethyl-2(3H)-imidazolethione) has been synthesized and characterized. The crystal and molecular structure of dmit·HBr has also been determined. The compound, C₅H₉BrN₂S, crystallizes in space groupP2₁/c with four formula units in a cell of dimensionsa= 7.331(1),b=7.744(2),c=14.626(4) Å, and=99.56(2)°. The calculated and observed densities are 1.678 and 1.68(2) g cm^–3, respectively. X-ray results along with physical characterization show this compound to be a molecular adduct of dmit and hydrogen bromide which is sensitive to air, light, and moisture. Specific conductivity (10^–3 M in PhNO₂), infrared, and¹H-NMR data have also been obtained. X-ray results reveal intermolecular contracts between S and Br to be primarily van der Waals in nature. Molecular units are linked through long zigzag Br-S-Br-S chains.