Conductivity of lithium gallium silicates

Lithium gallium silicates, Li_1−xGa_1−xSi_2+xO₆: 0.03 < x < 0.37, with a beta-spodumene structure, have a low Li⁺ ion conductivity, ca. 10⁻⁹ ω⁻¹ cm⁻¹ at 400 K rising to ca. 10⁻³ ω⁻¹ cm⁻¹ by 1000 K, that changes little with composition. The phase, LiGaSiO₄, with an alpha-eucryptite structure, exhibits mainly electronic conductivity, but at a low level, ca. 10⁻⁸ ω⁻¹ cm⁻¹ at 600 K, rising to ca. 10⁻⁵ ω⁻¹ cm⁻¹ at 1000 K.     

Die Eigenschwingungen des Metall-Hydratkomplexes in BeSO4·4H2O und BeSO4·4D2O

Infrared reflection spectra of single crystals of BeSO₄·4H₂O and BeSO₄·4D₂O have been obtained in polarized light at 300°K and at 14°K in the region between 4000 cm^?1 and 300 cm^?1. By a Kronig-Kramers analysis, the frequencies of the infrared active transitions have been calculated. These transitions are attributed to internal vibrations of the water molecules and sulfate ions and, in the region between 1000 cm^?1 and 300 cm^?1, especially to internal and external vibrations of the tetrahedral Be⁺⁺·4aqu-complexes. The vibrational modes of these complexes consist of a superposition of translational and librational modes of the water molecules and translational modes of the central Be⁺⁺-ion. The vibrational frequencies and normal modes of this complex have been calculated in a central-force model, and force-constants have been determined by fitting the calculated frequencies to the observed spectra. The calculations have shown that the modes, which comprise mainly translational motions of the water molecules, are strongly coupled with librational motions of the water molecules. On the other hand, there exist pure librational modes with practically no admixture of translational motions. The optimum sets of force constants for the BeSO₄·4H₂O crystal and the BeSO₄·4D₂O crystal differ in a manner which can be understood under the assumption that the dimensions of the Be(D₂O)₄ complex are about 0.1 Å larger than those of the Be(H₂O)₄ complex. Some arguments supporting this conclusion will be discussed.     

Far infrared reflection spectra due to lattice and free carrier in ZnxHg1−xSe

Far infrared reflection spectra of Zn_xHg_1−xSe with x = 0 to 0.4 showed characteristic of two TO-phonon modes behavior and the plasmon-LO phonon coupling in the region from 20 to 500 cm⁻¹ at 5 and 300 K. The composition dependence of TO modes on the frequency is linear for the HgSe-like mode TO₁ and constant for the ZnSe-like mode TO₂. The additional TO mode due to clustering effect is observed at 113 cm⁻¹. The plasmon-LO phonon coupled modes are explained well by our model taken into account the two-mode behavior and the contribution of interband transitions in dynamic dielectric function.     

Far-infrared quasi-local modes of ZnTe in CdTe

We report the very far-infrared absorption spectra of the mixed-crystals Cd_1-xZn_xTe for small x in the temperature range of 4.2K–150K and the wavenumber region of 20cm⁻¹–100cm⁻¹. The quasi-local mode induced by ZnTe in CdTe and CdTe-like 2TA two-phonon creations are observed, to be best of our knowledge, for the first time. The frequencies of the modes are estimated by using the mass-defect model combined with Green's functions calculations. Besides, the temperature dependence of the absorption peak is well explained in the light of the characteristics of the modes.     

Raman spectroscopic study of the antimonate mineral brandholzite Mg[Sb2(OH)12]·6H2O

Raman spectra of brandholzite Mg[Sb₂(OH)₁₂]·6H₂O were studied, complemented with infrared spectra, and related to the structure of the mineral. An intense Raman sharp band at 618 cm⁻¹ is attributed to the SbO symmetric stretching mode. The low‐intensity band at 730 cm⁻¹ is ascribed to the SbO antisymmetric stretching vibration. Low‐intensity Raman bands were found at 503, 526 and 578 cm⁻¹. Corresponding infrared bands were observed at 527, 600, 637, 693, 741 and 788 cm⁻¹. Four Raman bands observed at 1043, 1092, 1160 and 1189 cm⁻¹ and eight infrared bands at 963, 1027, 1055, 1075, 1108, 1128, 1156 and 1196 cm⁻¹ are assigned to δ SbOH deformation modes. A complex pattern resulting from the overlapping band of the water and hydroxyl units is observed. Raman bands are observed at 3240, 3383, 3466, 3483 and 3552 cm⁻¹; infrared bands at 3248, 3434 and 3565 cm⁻¹. The Raman bands at 3240 and 3383 cm⁻¹ and the infrared band at 3248 cm⁻¹ are assigned to water‐stretching vibrations. The two higher wavenumber Raman bands observed at 3466 and 3552 cm⁻¹ and two infrared bands at 3434 and 3565 cm⁻¹ are assigned to the stretching vibrations of the hydroxyl units. Observed Raman and infrared bands in the OH stretching region are associated with O‐H···O hydrogen bonds and their lengths 2.72, 2.79, 2.86, 2.88 and 3.0 Å (Raman) and 2.73, 2.83 and 3.07 Å (infrared). Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational properties of one- and two-mode behaviour in spinel type mixed systems Zn1−xCdxCr2S4

The infrared reflectivity spectra of spinel type mixed crystals Zn_1−xCd_xCr₂S₄ have been measured from 40 to 900 cm⁻¹. Four or five bands were observed at both end members in the region of intermediate composition. The three bands in higher energy show one-mode behaviour and the other two bands show two-mode behaviour. The concentration dependences of these mode frequencies are interpreted by a model proposed already, in which the 2 basic units and the 6 force constants are contained. By comparing the force constants associated with the Zn-site in several spinels, it is suggested that the two-mode behaviour arises from the large difference in the force constants between the two end members. The E_g (260 cm⁻¹) and T_2g (160 cm⁻¹) Raman modes for ZnCr₂S₄ were also observed and used for the determination of the force constants.     

Vibrational properties of graphene and graphene layers

The phonon dispersions of graphene and graphene layers are theoretically investigated within fifth‐nearest‐neighbor force‐constant approach. Based on their symmetry groups, the number of Raman‐ and infrared‐active modes at the Γ point is given. Interatomic force constants are recalculated by fitting them to experimental phonon energy dispersion curves. Wavenumbers of optically active modes are presented as a function of number of layers (n). Our calculated results reproduce well the experimental data of G peak for graphene (1587 cm⁻¹) and graphite (1581.6 cm⁻¹) and clearly give the relation that ω_G = 1581.6 + 11/(1 + n^1.6). Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl carbonate mineral voglite

Raman spectroscopy, complemented with infrared spectroscopy, was used to study the uranyl carbonate mineral voglite. The mineral has the formula Ca₂Cu²⁺ [(UO₂)(CO₃)₃](CO₃)^•6H₂O, and bands attributed to these vibrating units are readily identified in the Raman spectrum. Symmetric stretching modes at 836 and 1094 cm⁻¹ are assigned to ν₁(UO₂)²⁺ and ν₁(CO₃)²⁻ units, respectively. The ν₃ antisymmetric stretching modes of (UO₂)²⁺ are not observed in the Raman spectrum but may be readily observed in the infrared spectrum at 898 cm⁻¹. The ν₃ antisymmetric stretching mode of (CO₃)²⁻ is observed in the Raman spectrum at 1369 cm⁻¹ as a low intensity band as is also the ν₃(CO₃)²⁻ infrared modes at 1362, 1425, 1509 and 1566 cm⁻¹. No ν₂(CO₃)²⁻ Raman bending modes are observed for voglite. The Raman band at 749 cm⁻¹ and the two infrared bands at 747 and 709 cm⁻¹ are assigned to the ν₄(CO₃)²⁻ bending modes. U O bond and O H…O bond lengths in the structure of voglite were inferred from the infrared and Raman spectra. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman spectroscopy of halogen‐containing carbonates

Raman spectroscopy complemented with infrared spectroscopy has been used to study a series of selected natural halogenated carbonates from different origins, including bastnasite, parisite and northupite. The position of CO₃²⁻ symmetric stretching vibration varies with the mineral composition. An additional band for northupite at 1107 cm⁻¹ is observed. Raman spectra of bastnasite, parisite and northupite show single bands at 1433, 1420 and 1554 cm⁻¹, respectively, assigned to the ν₃ (CO₃)²⁻ asymmetric stretching mode. The observation of additional Raman bands for the ν₃ modes for some halogenated carbonates is significant in that it shows distortion of the CaO₆ octahedron. No ν₂ Raman bending modes are observed for these minerals. The band is observed in the infrared spectra, and multiple ν₂ modes at 844 and 867 cm⁻¹ are observed for parisite. A single intense infrared band is found at 879 cm⁻¹ for northupite. Raman bands are observed forthe carbonate ν₄ in‐phase bending modes at 722 cm⁻¹ for bastnasite, 736 and 684 cm⁻¹ for parisite and 714 cm⁻¹ for northupite. Multiple bands are observed in the OH stretching region for selected bastansites and parisites, indicating the presence of water and OH units in the mineral structure. The presence of such bands brings into question the actual formula of these halogenated carbonate minerals. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the magnesium carbonate mineral hydromagnesite (Mg5[(CO3)4(OH)2]· 4H2O)

Magnesium minerals are important for understanding the concept of geosequestration. One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy. A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm⁻¹, attributed to the CO₃²⁻ν₁ symmetric stretching mode. A series of infrared bands at 1387, 1413 and 1474 cm⁻¹ are assigned to the CO₃²⁻ν₃ antisymmetric stretching modes. The CO₃²⁻ν₃ antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm⁻¹. A series of Raman bands at 708, 716, 728 and 758 cm⁻¹ are assigned to the CO₃²⁻ν₂ in‐plane bending mode. The Raman spectrum in the OH stretching region is characterized by bands at 3416, 3516 and 3447 cm⁻¹. In the infrared spectrum, a broad band is found at 2940 cm⁻¹, which is assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm⁻¹ are attributed to MgOH stretching modes. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the multi‐anion mineral dixenite CuMn2+14Fe3+(AsO3)5(SiO4)2(AsO4)(OH)6

The mixed anion mineral dixenite has been studied by Raman spectroscopy, complemented with infrared spectroscopy. The Raman spectrum of dixenite shows bands at 839 and 813 cm⁻¹ assigned to the (AsO₃)³⁻ symmetric and antisymmetric stretching modes. The most intense Raman band of dixenite is the band at 526 cm⁻¹ and is assigned to the ν₂ AsO₃³⁻ bending mode. DFT calculations enabled the calculation of the position of AsO₂²⁻ symmetric stretching mode at 839 cm⁻¹, the antisymmetric stretching mode at 813 cm⁻¹, and the deformation mode at 449 cm⁻¹. The Raman bands at 1026 and 1057 cm⁻¹ are assigned to the SiO₄²⁻ symmetric stretching vibrations and those at 1349 and 1386 cm⁻¹ to the SiO₄²⁻ antisymmetric stretching vibrations. Both Raman and infrared spectra indicate the presence of water in the structure of dixenite. This brings into question the commonly accepted formula of dixenite as CuMn²⁺₁₄Fe³⁺(AsO₃)₅(SiO₄)₂(AsO₄)(OH)₆. The formula may be better written as CuMn²⁺₁₄Fe³⁺(AsO₃)₅(SiO₄)₂(AsO₄)(OH)₆·xH₂O. Copyright © 2009 John Wiley & Sons, Ltd.     

Polarized Raman spectra of brushite (CaHPO4.2H2O) crystal. Investigation of the phosphate stretching modes,study of the LOTO splitting

Polarized Raman measurements were recorded on a monoclinic brushite (CaHPO₄.2H₂O) crystal in the 800–1200 cm⁻¹ spectral range, corresponding to the P O stretching modes. This study is a continuation of the investigation of the phosphate stretching modes observed in polarized infrared reflectance spectra of brushite crystal. In such ionic non‐centrosymmetric crystals, the splitting between the transverse and longitudinal components of the optic vibrations was observed in the polarized Raman spectra recorded at several scattering geometries. A″ symmetry modes of the brushite crystal were measured. Using a simple model based on the symmetry of the PO₄ group, the Raman intensities of the stretching modes are calculated and compared with experimental bands. Copyright © 2016 John Wiley & Sons, Ltd.     

Raman spectroscopy of gallium‐ and zinc‐based hydrotalcites

Insight into the unique structure of hydrotalcites (HTs) has been obtained using Raman spectroscopy. Gallium‐containing HTs of formula Zn₄ Ga₂(CO₃)(OH)₁₂ · xH₂O (2:1 ZnGa‐HT), Zn₆ Ga₂(CO₃)(OH)₁₆ · xH₂O (3:1 ZnGa‐HT) and Zn₈ Ga₂(CO₃)(OH)₁₈ · xH₂O (4:1 ZnGa‐HT) have been successfully synthesised and characterised by X‐ray diffraction (XRD) and Raman spectroscopy. The d(003) spacing varies from 7.62 Å for the 2:1 ZnGa‐HT to 7.64 Å for the 3:1 ZnGa‐HT. The 4:1 ZnGa‐HT showed a decrease in the d(003) spacing, compared to the 2:1 and 3:1 compounds. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised gallium‐containing HTs. Raman bands observed at around 1050, 1060 and 1067 cm⁻¹ are attributed to the symmetric stretching modes of the (CO₃²⁻) units. Multiple ν₃ (CO₃²⁻) antisymmetric stretching modes are found between 1350 and 1520 cm⁻¹, confirming multiple carbonate species in the HT structure. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm⁻¹ and assigned to the ν₄ (CO₃²⁻) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2010 John Wiley & Sons, Ltd.     

A Raman spectroscopic study of the different vanadate groups in solid‐state compounds—model case: mineral phases vésigniéite [BaCu3(VO4)2(OH)2] and volborthite [Cu3V2O7(OH)2·2H2O]

Raman spectroscopy has been used to study vanadates in the solid state. The molecular structure of the vanadate minerals vésigniéite [BaCu₃(VO₄)₂(OH)₂] and volborthite [Cu₃V₂O₇(OH)₂·2H₂O] have been studied by Raman spectroscopy and infrared spectroscopy. The spectra are related to the structure of the two minerals. The Raman spectrum of vésigniéite is characterized by two intense bands at 821 and 856 cm⁻¹ assigned to ν₁ (VO₄)³⁻ symmetric stretching modes. A series of infrared bands at 755, 787 and 899 cm⁻¹ are assigned to the ν₃ (VO₄)³⁻ antisymmetric stretching vibrational mode. Raman bands at 307 and 332 cm⁻¹ and at 466 and 511 cm⁻¹ are assigned to the ν₂ and ν₄ (VO₄)³⁻ bending modes. The Raman spectrum of volborthite is characterized by the strong band at 888 cm⁻¹, assigned to the ν₁ (VO₃) symmetric stretching vibrations. Raman bands at 858 and 749 cm⁻¹ are assigned to the ν₃ (VO₃) antisymmetric stretching vibrations; those at 814 cm⁻¹ to the ν₃ (VOV) antisymmetric vibrations; that at 508 cm⁻¹ to the ν₁ (VOV) symmetric stretching vibration and those at 442 and 476 cm⁻¹ and 347 and 308 cm⁻¹ to the ν₄ (VO₃) and ν₂ (VO₃) bending vibrations, respectively. The spectra of vésigniéite and volborthite are similar, especially in the region of skeletal vibrations, even though their crystal structures differ. Copyright © 2011 John Wiley & Sons, Ltd.     

A far-infrared investigation of cathodochromic sodalite

Sodalite absorption bands in the 50–350 cm⁻¹ region were studied using Fourier transform spectroscopy. Vibrational modes were identified using chemical substitution, H₂ and vacuum-annealing, and coloration studies. A bromosodalite band at 294 cm⁻¹ was assigned to an Si—O—Al mode based on Ge substitutions for Si. A bromosodalite band at 200 cm⁻¹ is assigned to an Na—cage vibration based on previous H₂annealing studies and chemical substitution of Ge for Si, Ga for Al and Cl and I for Br. A 107 cm⁻¹ band is the Na—Br related vibration, and substitution of 100% Cl for Br moved this band to 111 cm⁻¹, H₂ and vacuum-annealing studies show a correlation between the amount of Br removed from bromosodalite during annealing and the area of the 107 cm⁻¹ band. A band at 68 cm⁻¹ is the Na—Br mode based on 100% substitution of Cl for Br. Coloration studies in the 50–150 cm⁻¹ region show no changes attributable to F-center formation.     

FT‐Raman,FT‐IR spectra and DFT calculations on monomeric and dimeric structures of 5‐fluoro‐ and 5‐chloro‐salicylic acid

The experimental and theoretical study on the structures and vibrations of 5‐fluoro‐salicylic acid and 5‐chloro‐salicylic acid (5‐FSA and 5‐ClSA, C₇H₅FO₃ and C₇H₅ClO₃) is presented. The Fourier transform infrared spectra (4000–400 cm⁻¹) and the Fourier transform Raman spectra (4000–50 cm⁻¹) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecular O H···O hydrogen bond. The geometrical parameters and energies of 5‐FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6‐311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5‐FSA and 5‐ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5‐FSA and 5‐ClSA monomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wavenumbers showed the best agreement with the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

High-resolution infrared spectrum of hydrogen peroxide: The ν6 fundamental band

The infrared spectrum of the ν₆ asymmetric deformation band of hydrogen peroxide (H₂O₂) was studied in the region 1100–1350 cm⁻¹ using the two techniques of Fourier transform spectroscopy at 0.02 cm⁻¹ resolution and tunable diode laser spectroscopy at Doppler-limited resolution. Details of the wavelength calibration procedures adopted are discussed. For the first time, accurate values of the molecular parameters of this torsionally doubled, vibrational band were obtained. A total of 708 assigned transitions have been analyzed to yield a set of 14 rovibrational constants for the lower torsion-vibration level (SD = 0.00487 cm⁻¹) and 13 rovibrational constants for the upper torsion-vibration level (SD = 0.00382 cm⁻¹). These hybrid bands are primarily A type with band centers at 1264.5812 ± 0.0009 and 1273.6830 ± 0.0009 cm⁻¹. Because of the absence of observed perturbations, the derived molecular constants can be used to calculate transition frequencies with a high degree of accuracy up to K_a = 6.     

Type III - Type I transition and strain-effect in Hg1−xCdxTeCdTe and Hg1−xZnxTeCdTe superlattices

In this paper, the results of Hg_1−xZn_xTeCdTe strained layer superlattices grown by MBE are reported, and compared to Hg_1−xCd_xTeCdTe superlattices. Both Type III and Type I Hg_1−xZn_xTeCdTe superlattices with different strain have been grown on CdTe(111)B/GaAs(100) and CdTe(100)/GaAs(100) substrates and characterized by electron, X-ray diffraction, infrared transmission and Hall measurements. The values of hole mobility between 5×10³ up to 2×10⁴cm²v⁻¹s⁻¹ at T = 23K along (111)B growth orientation and up to 4.9×10⁴cm²v⁻¹s⁻¹ at T = 5K along (100) growth orientation are obtained for Type III superlattices whereas in Type I superlattices, the hole mobility is between 200–300cm²v⁻¹s⁻¹. This drastic change in the hole mobility between Type III and Type I superlattices along with the role of the strain are discussed in this paper.     

Raman spectrum of decrespignyite [(Y,REE)4Cu(CO3)4Cl(OH)5·2H2O] and its relation with those of other halogenated carbonates including bastnasite,hydroxybastnasite, parisite and northupite

Raman spectroscopy complemented with infrared spectroscopy has been used to study the rare‐earth‐based mineral decrespignyite [(Y,REE)₄Cu(CO₃)₄Cl(OH)₅· 2H₂O] and the spectrum compared with the Raman spectra of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of decrespignyite displays three bands at 1056, 1070 and 1088 cm⁻¹ attributed to the CO₃²⁻ symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of the CO₃²⁻ symmetric stretching vibration varies with the mineral composition. The Raman spectrum of decrespignyite shows bands at 1391, 1414, 1489 and 1547 cm⁻¹, whereas the Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554 cm⁻¹, respectively, assigned to the ν₃ (CO₃)²⁻ antisymmetric stretching mode. The observation of additional Raman bands for the ν₃ modes for some halogenated carbonates is significant in that it shows distortion of the carbonate anion in the mineral structure. Four Raman bands are observed at 791, 815, 837 and 849 cm⁻¹, which are assigned to the (CO₃)²⁻ν₂ bending modes. Raman bands are observed for decrespignyite at 694, 718 and 746 cm⁻¹ and are assigned to the (CO₃)²⁻ν₄ bending modes. Raman bands are observed for the carbonate ν₄ in‐phase bending modes at 722 cm⁻¹ for bastnasite, 736 and 684 cm⁻¹ for parisite and 714 cm⁻¹ for northupite. Multiple bands are observed in the OH stretching region for decrespignyite, bastnasite and parisite, indicating the presence of water and OH units in the mineral structure. Copyright © 2011 John Wiley & Sons, Ltd.     

Integrated infrared intensities in NH3

The integrated infrared intensities of the fundamental modes of NH₃ have been measured by the Wilson-Wells-Penner-Weber method. The intensities were found to be 43.9 ± 0.6, 567.6 ± 9.4 and 110.5 ± 2.0 atm^-1 cm^-2 (standard temperature and pressure) for the ν₁ + ν₃, ν₂ and ν₄ bands, respectively.