Ν4 Bending Modes Research Articles

High-pressure study on calcium azide (Ca(N3)2): the bending of the azide ions stabilizes the structure

Abstract The high-pressure structure and elastic properties of calcium azide (Ca(N3)2) were investigated using in-situ high-pressure X-ray diffraction and Raman scattering up to 54 GPa and 19 GPa, respectively. The compressibility of Ca(N3)2 changed as the pressure increased, and no phase transition occurred within the pressure from ambient pressure up to 54 GPa. The measured zero-pressure bulk modulus of Ca(N3)2 is higher than that of other alkali metal azides, due to differences in the ionic character of their metal-azide bonds. Using CASTEP, all vibration modes of Ca(N3)2 were accurately identified in the vibrational spectrum at ambient pressure. In the high-pressure vibration study, several external modes(ext.) and internal bending modes(ν2) of azide anions(N3 -) softened up to ~7 GPa and then hardened beyond that pressure. This evidence is consistent with the variation observed in the FE -fE data analyzed from the XRD result, where the slope of the curve changes at 7.1 GPa. The main behaviors under pressure are the alternating compression, rotation, and bending of N3 - ions. The bending behavior makes the structure of Ca(N3)2 more stable under pressure.

Ro-vibrational Spectrum of Linear Dialuminum Monoxide (Al2O) at 10 μm.

Dialuminum monoxide, Al2O, has been investigated in the laboratory at mid-IR wavelengths around 10 μm at high spectral resolution. The molecule was produced by laser ablation of an aluminum target with the addition of gaseous nitrous oxide, N2O. Subsequent adiabatic cooling of the gas in a supersonic beam expansion led to rotationally cold spectra. In total, 848 ro-vibrational transitions have been assigned to the fundamental asymmetric stretching mode ν3 and to five of its hot bands, originating from excited levels of the ν1 symmetric stretching mode and the ν2 bending mode. The measurements encompass 11 vibrational energy states (v1 v2l v3). The ro-vibrational transitions show spin statistical line intensity alternation of 7:5, which is caused by two identical aluminum nuclei of spin I = 5/2 at both ends of the centrosymmetric molecule of structure Al-O-Al. The less effective cooling of vibrational states in the supersonic beam expansion allowed measurement of transitions in excited vibrational states at energies of 1000 cm-1 and higher, while rotational levels within vibrational modes exhibited thermal population, with rotational temperatures around Trot = 115 K. Molecular parameters for 11 vibrational states were derived, including rotation and centrifugal distortion constants and l-type doubling constants for the states (v1 v2l v3) = (0 11 0) and (0 11 1) and an l-type resonance between the states (0 20 0) - (0 22 0) and (0 20 1) - (0 22 1). From the experimental results, rotational correction terms and the equilibrium bond length re were derived. The measurements were supported and guided by high-level quantum-chemical calculations that agree well with the derived experimental results.

In-Situ Single Crystal XRD and Raman Spectra Investigation of (Mg, Fe, Mn)CO3 at Various Temperatures

The in-situ X-ray diffraction (XRD) and Raman spectra of synthetic (Mg, Fe, Mn)CO3 single crystals for (Mg0.37Fe0.31Mn0.32)CO3, (Mg0.49Fe0.51)CO3, (Fe0.47Mn0.53)CO3, and (Mg0.50Mn0.50)CO3 were investigated up to 871 K. Lattice parameters and the volumetric thermal expansion coefficients were achieved, demonstrating an inherent anisotropy of c/a near to 3.0. The Raman spectra of our intermediate components all exhibit a negative temperature dependence similar to that of the end members. The temperature dependence of the external modes T, L, anti-symmetric stretching mode ν3, and out-of-plane bending mode 2ν2 is generally more prominent than the in-plane bending mode ν4 and symmetric stretching mode ν1 except for siderite FeCO3. Combining thermal expansion coefficients αV with the relative changes in frequency δνi/δT of Raman spectra, the average thermodynamic Grüneisen parameters (γth) for (Mg0.37Fe0.31Mn0.32)CO3, (Fe0.47Mn0.53)CO3, (Mg0.50Mn0.50)CO3, MgCO3, and MnCO3 were obtained as 1.18, 1.36, 1.34, 1.13, and 1.53, respectively. The relationship between Fe2+ and Mn2+ contents and γth illustrates that the concentration of Fe2+ causes a negative effect while the concentration of Mn2+ causes a positive effect on γth. These results could provide a reference for the contribution of Fe2+ and Mn2+ on the structural and thermodynamic properties of (Mg, Fe, Mn)CO3 carbonates.

The bending of C3: Experimentally probing the [formula omitted]-type doubling and resonance

C3, a pure carbon chain molecule that has been identified in different astronomical environments, is considered a good probe of kinetic temperatures through observation of transitions involving its low-lying bending mode (ν2) in its ground electronic state. The present laboratory work aims to investigate this bending mode with multiple quanta of excitation by combining recordings of high resolution optical and infrared spectra of C3 produced in discharge experiments. The optical spectra of rovibronic (Ã1Πu−X̃1Σg+) transitions have been recorded by laser induced fluorescence spectroscopy using a single longitude mode optical parametric oscillator as narrow bandwidth laser source at the University of Science and Technology of China. 36 bands originating from X̃(0v20), v2=0−5, are assigned. The mid-infrared spectrum of the rovibrational ν3 band has been recorded by Fourier-transform infrared spectroscopy using a globar source on the AILES beamline of the SOLEIL synchrotron facility. The spectrum reveals hot bands involving up to 5 quanta of excitation in ν2. From combining analyses of all the presently recorded spectra and literature data, accurate rotational parameters and absolute energy levels of C3, in particular for states involving the bending mode, are determined. A single PGOPHER file containing all available data involving the X̃ and à states (literature and present study) is used to fit all the data. The spectroscopic information derived from this work enables new interstellar searches for C3, not only in the infrared and optical regions investigated here but also notably in the ν2 band region (around 63 cm−1) where vibrational satellites can now be accurately predicted. This makes C3 a universal diagnostic tool to study very different astronomical environments, from dark and dense to translucent clouds.

N2O–Ar and N2O–Kr: Intermolecular vibrations of N2O–Kr and symmetry breaking of the N2O bending mode in the presence of a rare gas

Rotationally-resolved infrared spectra of N2O–Ar and N2O–Kr are studied in the region of the N2O ν1 vibration (≈2224 cm−1) using a tunable Quantum Cascade laser source to probe a pulsed supersonic jet. The N2O–Kr ν1 fundamental band is re-analyzed, together with previous ν3 band data, using a unified scheme to fit the (small) observed Kr isotope splittings. This scheme is then transferred to analyze the bending combination band of N2O–Kr near 2257 cm−1 where isotope effects are much larger due to stretch-bend interactions. As a result, N2O–Kr intermolecular bend (33.29 cm−1) and stretch (34.48 cm−1) frequencies are directly determined for the first time. Weak spectra are detected for both N2O–Ar and –Kr corresponding to the (ν1, ν2l2, ν3) = (1110) ← (0110) hot band of N2O. Their analysis yields the magnitude of the splitting of the N2O ν2 bending mode into in-plane and out-of-plane components. These splittings are found to be significantly smaller than those observed in the analogous CO2-containing dimers.

New infrared spectra of CO2 – Ne: Fundamental for CO2 –22Ne isotopologue, intermolecular bend, and symmetry breaking of the intramolecular CO2 bend

The infrared spectrum of CO2-Ne complex is studied in the region of the CO2 ν3 fundamental vibration. The vibrational fundamentals for both CO2-20Ne and CO2-22Ne are analyzed in combination with available microwave data. In addition, combination bands involving the intermolecular bending mode are observed, leading to the determination of the bending frequency. For the hot band CO2 transition, (0111) ← (0110), detection of the weak CO2-Ne spectrum reveals the symmetry breaking of the CO2 ν2 bending mode induced by the Ne atom, with the out-of-plane component determined to lie 0.057 cm−1 higher in energy than the in-plane component.

Theoretical rovibronic spectroscopy of the calcium monohydroxide radical (CaOH).

The rovibronic (rotation-vibration-electronic) spectrum of the calcium monohydroxide radical (CaOH) is of interest to studies of exoplanet atmospheres and ultracold molecules. Here, we theoretically investigate the Ã2Π-X̃2Σ+ band system of CaOH using high-level ab initio theory and variational nuclear motion calculations. New potential energy surfaces (PESs) are constructed for the X̃2Σ+ and Ã2Π electronic states along with Ã-X̃ transition dipole moment surfaces (DMSs). For the ground X̃2Σ+ state, a published high-level ab initio PES is empirically refined to all available experimental rovibrational energy levels up to J = 15.5, reproducing the observed term values with a root-mean-square error of 0.06 cm-1. Large-scale multireference configuration interaction calculations using quintuple-zeta quality basis sets are employed to generate the Ã2Π state PESs and Ã-X̃ DMSs. Variational calculations consider both Renner-Teller and spin-orbit coupling effects, which are essential for a correct description of the spectrum of CaOH. Computed rovibronic energy levels of the Ã2Π state, line list calculations up to J = 125.5, and an analysis of Renner-Teller splittings in the ν2 bending mode of CaOH are discussed.

Systematic Raman Spectroscopic Study of the Isomorphy Between the Arsenate Minerals Roselite, Wendwilsonite, Zincroselite, Brandtite, and Rruffite.

In nature, numerous minerals are known with the general formula X2M(TO4)2·2(H2O) and an important group is formed by minerals with T = As. Most of these occur as minor or trace minerals in environments such as hydrothermal alterations of primary sulfides and arsenides. X-ray photoelectron spectroscopy and Raman spectroscopy have been utilized to study the chemistry and crystal structure of the roselite subgroup minerals, Ca2M(AsO4)2·2H2O (with M = Co, Mg, Mn, Zn, and Cu). The AsO4 stretching region exhibited minor differences between the roselite subgroup minerals, which can be explained by the ionic radius of the cation substituting on the M position in the structure. Multiple AsO4 antisymmetric stretching and bending modes were found, pointing to a tetrahedral symmetry reduction. Bands around 450 cm-1 were attributed to ν4 bending modes. Several bands in the 300-350 cm-1 region attributed to ν2 bending modes also provide evidence of symmetry reduction of the AsO4 anion. Two broad bands for roselite were found around 3330 and 3120 cm-1 and were attributed to the OH stretching bands of crystal water. These bands are accompanied by two bands around 1700 and 1610 cm-1 attributed to the corresponding OH-bending modes. In conclusion, both XPS and Raman spectroscopy are valuable nondestructive analytical tools to characterize these secondary arsenate minerals. X-ray photoelectron spectroscopy and Raman microspectroscopy allow the chemistry and molecular structure of the roselite group minerals to be studied in a nondestructive way. The minerals in the roselite subgroup are easily distinguished based on their chemical composition as determined by XPS. As expected for minerals with the same crystal structure, similarities exist in the Raman spectra, sufficient differences exist to be able to identify these minerals.

IR multiple photon dissociation spectroscopy of MO2 + (M = V, Nb, Ta).

A laser vaporization cluster source is coupled to the Fourier-transform ion cyclotron resonance mass spectrometer beamline of the free-electron laser for intracavity experiments. Gas phase metal ions and their oxides (VO2 +, NbO2 +, and TaO2 +) are formed and spectroscopically characterized using IR multiple-photon dissociation spectroscopy via loss of atomic oxygen and overcoming fragmentation energies of 3 eV-6 eV. The signal is observed for all MO2 + fundamental modes: the symmetric and anti-symmetric ν1 and ν3 stretch modes in the 900 cm-1-1000 cm-1 range and the ν2 bending mode in the 300 cm-1-450 cm-1 range. A remarkable substructure is observed for the bending vibration, which is at least partly due to the rovibrational substructure.

Stimulated Raman Scattering in Yttrium, Gadolinium, and Calcium Orthovanadate Crystals with Single and Combined Frequency Shifts under Synchronous Picosecond Pumping for Sub-Picosecond or Multi-Wavelength Generation around 1.2 µm

Comparative investigation of stimulated Raman scattering (SRS) characteristics in the YVO4, GdVO4, and Ca3(VO4)2 orthovanadate crystals at both low and high frequency anionic group vibrations is presented. It was found that GdVO4 is the most perspective for SRS generation on both the ν1 stretching and ν2 bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous picosecond pumping. It is as a result of GdVO4‘s widest linewidth (17cm−1) of the homogeneously broadened scheelite-type component of the bending ν2 Raman line that led to the strongest SRS pulse shortening down to the dephasing time of the widest (scheelite-type) Raman mode at the secondary intracavity short-shifted SRS conversion. It allowed us to achieve SRS pulses with sub-picosecond duration under tens-of-picoseconds pumping due to the strongest 42-fold pulse shortening. Using the Ca3(VO4)2 crystal with essentially wider Raman lines (~50cm−1) did not allow us to generate SRS pulses shorter than 1 ps. It can be explained by inhomogeneous broadening of the Raman lines in Ca3(VO4)2 because of its structural disordering. Using the measured SRS pulse duration, the homogeneous broadening of the inhomogeneously broadened bending Raman line of Ca3(VO4)2 was estimated to be ~9cm−1. Among the orthovanadate crystals, the YVO4 crystal with the highest Raman gain and with homogeneously broadened Raman lines allowed us to realize the most efficient SRS lasing and SRS pulse shortening truly down to inverse half-width of the bending Raman line.

Computational and Spectroscopic Studies of Carbon Disulfide.

The vibrational spectroscopy of CS2 has been investigated many times in all three phases. However, there is still some ambiguity about the location of two of the modes in the solid state. The aim of this work was to locate all of the modes by inelastic neutron scattering (INS) spectroscopy, (which has no selection rules), and to use periodic density functional theory to provide a complete and unambiguous assignment of all the modes in the solid state. A comparison of the observed and calculated INS spectra shows generally good agreement. All four of the ν2 bending mode components are calculated to fall within 14 cm−1. Inspection of the spectrum shows that there are no bands close to the intense feature at 390 cm−1 (assigned to ν2); this very strongly indicates that the Au mode is within the envelope of the 390 cm−1 band. Based on a simulation of the band shape of the 390 cm−1 feature, the most likely position of the optically forbidden component of the ν2 bending mode is 393 ± 2 cm−1. The calculations show that the optically inactive Au translational mode is strongly dispersed, so it does not result in a single feature in the INS spectrum.

Gas-Phase Isotopic Fractionation Study of Singly and Doubly Deuterated Isotopologues of Water in the H-D Exchange Reaction by Cavity Ring-Down Spectroscopy.

The underlying mechanisms of the triple-oxygen (16O, 17O, and 18O) isotopic content of deuterated (D) isotopologues of water in H-D exchange reactions in the gas phase remain elusive. Herein, we have demonstrated a high-resolution gas-phase spectral analysis of doubly (D2O) and singly (HDO) deuterated isotopologues of water in the region around 7.8 μm using quantum cascade laser-based cavity ring-down spectroscopy. Isotopic fractionations among doubly and singly deuterated species of water, D216O, HD16O, HD17O, and HD18O, in the gas phase were carried out by probing the fundamental and hot band transitions in the ν2 (bending) mode of D2O and the fundamental ν2 transitions for the other water isotopes. We subsequently investigated the fractionations of different D-enriched water isotopologues for the H-D exchange reaction using various mixtures of D2O in H2O. We explored the potential role of triple-oxygen isotopic contents through enrichments and depletions of HD16O, HD17O, and HD18O, involved in the H-D reaction. Our first clear, direct, and quantitative experimental evidence reveals a new picture of gas-phase isotopic fractionation chemistry in a mixture of light and heavy water (H2O-D2O).

In Situ Raman Spectroscopic Studies of Liquid Carbon Tetrachloride (CCl4) Under Static and Laser-Driven Shock Compression.

High pressure (up to ∼2.2 GPa) Raman scattering studies were performed in carbon tetrachloride (CCl4) under static and dynamic compressions using diamond anvil cell (DAC) and laser-driven shock methods, respectively, and their results are compared. The laser-driven shock experiments were conducted in a glass-confined target geometry. The symmetric stretching mode ν1, symmetric bending mode ν2, and asymmetric bending mode ν4 blueshifts with pressure. Mode Gruneisen parameters were obtained for the above Raman modes. Time-resolved Raman spectroscopic (TRRS) studies were performed under laser-driven shock compression at different delay times. Shock velocity deduced from the intensity ratios of Raman signal scattered from unshocked and shocked regions of symmetric stretching mode is in agreement with the one obtained from one-dimensional hydrodynamic simulations.

Spectroscopic characterization of rare hydrated ammonium borate mineral larderellite

Two samples of larderellite (NH4)B5O7(OH)2·H2O from Monte Rotonda (Italy) have been studied. Spectroscopic methods, like infrared and Raman spectroscopy, were used in combination with thermal analysis and X-ray diffraction. The main objective was vibrational characteristic of research mineral and, based on the obtained results, test how the long storage of minerals affect their structure. Raman and infrared spectroscopy confirm the presence of tetrahedral and trigonal boron structural units in the investigated samples. The most intensive Raman band is located at 149 cm−1 and is assigned to lattice vibration. The most intensive infrared bands, located at 1209 and 1273 cm−1, are ascribed as in-plane modes (δ) of BOH. Bands associated with water bending mode (ν2) and stretching vibration (ν1) are observed at 1668 cm−1 (IR) and in the 3000–3500 cm−1 region (both Raman and IR spectrum). Thermal analysis showed differences between two research samples of larderellite connected with presence of adsorption water, that can indicate influence of conditions of minerals storage on properties of mineral.

Ab initio potential energy surface and vibration-rotation energy levels of disilicon carbide, CSi2

The accurate potential energy surface of disilicon carbide, CSi2, in its ground electronic state X∼1A1 has been determined from ab initio calculations using the coupled-cluster approach in conjunction with the correlation-consistent basis sets up to septuple-zeta quality. The core-electron correlation, higher-order valence-electron correlation, scalar relativistic, and adiabatic effects were taken into account. The potential energy barrier to the linear SiCSi configuration was predicted to be 832cm−1. The vibration-rotation energy levels of the CSi2, 13CSi2, CSi29Si, and CSi30Si isotopologues were predicted using a variational approach. The experimental vibration-rotation energy levels of the main isotopologue were reproduced to high accuracy. In particular, long vibrational progressions in the highly anharmonic SiCSi bending mode ν2 originating from the ground vibrational state of CSi2 are reproduced to within about 2.4cm−1 on average, close to the experimental accuracy.

Raman spectroscopy of various phosphate minerals and occurrence of tuite in the Elga IIE iron meteorite

The Raman spectra of phosphate minerals: apatite, merrillite, panethite, brianite, czochralskiite, maricite, new phosphate with composition of Na2Fe(Mg,Ca)(PO4)2 and high‐pressure phase tuite from the Elga IIE iron meteorite are characterized. Panethite, brianite, czochralskiite and new Na‐Fe phosphate were described for the first time. The basic features of all studied phosphates include strong ν1 symmetric stretching mode of PO43− ions at 950–990 cm−1, antisymmetric ν3 vibrations in the 1000–1175 cm−1 region and weak bands in the 400–500 cm−1 region, which correspond to ν2 bending mode and in the 550–640 cm−1 region, related to ν4 bending mode. Weak bands at less than 300 cm−1 represent lattice modes. Most of the studied phosphates have three non‐equivalent positions of phosphorus atoms in the crystal structures and can be derived from glaserite, K3Na(SO4)2, arrangement. Two or three of non‐equivalent [PO4] tetrahedra typically correspond to two or three strong bands in the region of ν1 vibrations. High‐pressure mineral tuite has similar composition and was formed after merrillite. P‐O vibrations in equivalent [PO4] tetrahedra produce major Raman band of tuite at 972 cm−1. The Elga parent‐body experienced a shock pressure of at least 12–15 GPa according to minimum pressures of tuite formation in the static high‐pressure experiments. This is the first finding of tuite in iron meteorites and the only second finding of high‐pressure mineral in them. Copyright © 2017 John Wiley & Sons, Ltd.

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite

AbstractA multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, singlecrystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. Thechemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)Σ=6.06(Mg0.01Ca1.93Ba0.40)Σ=2.34(Fe0.023+Al10.55Si21.38)Σ=31.9O64·19.6H2O,compatible with the ideal chemical formula K6Ca2[Al10Si22O64]·20H2O.Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5),b = 14.111(5), c = 9.943(3) Å at 100 K). Refinement converged with four cationic sites and six H2O sites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/Al-distribution. The Raman spectrum of merlinoite (collected between 100and 4000 cm–1) is dominated by a doublet of bands between 496–422 cm–1, assigned to tetrahedral T–O–T symmetric bending modes. T–O–T antisymmetric stretching is also observed; stretching and bending modes of the H2Omolecules are only clearly visible when using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm–1, assigned to the first overtone of the O–H stretching mode, and a band at 5209 cm–1, due to the combination of H2Ostretching and bending modes. Avery broad and convoluted absorption, extending from 3700 to 3000 cm–1 occurs in the H2O stretching region, while the ν2 bending mode of H2O is found at 1649 cm–1. The powder mid-infraredspectrum of merlinoite between 400–1300 cm–1 is dominated by tetrahedral T–O–T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites,which are often confused due to their close similarity.

SEM, EDX and vibrational spectroscopic study of the carbonate mineral donnayite-(Y) NaCaSr3Y(CO3)6·3H2O

The mineral donnayite-(Y) has been studied by scanning electron microscopy with chemical analysis using EDX and vibrational spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the donnayite-(Y) structure. Intense sharp bands at 464, 479 and 508 cm−1 are assigned to YO stretching modes. Raman bands at 765 and 775 cm−1 are assigned to the CO32−ν4 bending modes and Raman bands at 589, 611, 674 and 689 cm−1 are assigned to the CO32−ν2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water in different molecular environments in the structure of donnayite-(Y).

SEM, EDX and Raman and infrared spectroscopic study of brianyoungite Zn3(CO3,SO4)(OH)4 from Esperanza Mine, Laurion District, Greece

The mineral brianyoungite, a carbonate–sulphate of zinc, has been studied by scanning electron microscopy (SEM) with chemical analysis using energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the brianyoungite structure. Intense Raman band at 1056cm−1 with shoulder band at 1038cm−1 is assigned to the CO32− ν1 symmetric stretching mode. Two intense Raman bands at 973 and 984cm−1 are assigned to the symmetric stretching modes of the SO42− anion. The observation of two bands supports the concept of the non-equivalence of sulphate units in the brianyoungite structure. Raman bands at 704 and 736cm−1 are assigned to the CO32− ν4 bending modes and Raman bands at 507, 528, 609 and 638cm−1 are assigned to the CO32− ν2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water and hydroxyl units in different molecular environments in the structure of brianyoungite. Vibrational spectroscopy enhances our knowledge of the molecular structure of brianyoungite.

Raman and infrared spectroscopic characterization of the arsenate‐bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite

The minerals clinotyrolite and fuxiaotuite are discredited in terms of the mineral tangdanite. The mixed anion mineral tangdanite Ca2Cu9(AsO4)4(SO4)0.5(OH)9 9H2O has been studied using a combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. These bands are assigned to water and hydroxyl stretching vibrations. Two intense Raman bands at 837 and approximately 734 cm−1 are assigned to the ν1 (AsO4)3− symmetric stretching and ν3 (AsO4)3− antisymmetric stretching modes. Infrared bands at 1023 cm−1 are assigned to the (SO4)2− ν1 symmetric stretching mode, and infrared bands at 1052, 1110 and 1132 cm−1 assigned to (SO4)2− ν3 antisymmetric stretching modes, confirming the presence of the sulphate anion in the tangdanite structure. Raman bands at 593 and 628 cm−1 are attributed to the (SO4)2− ν4 bending modes. Low‐intensity Raman bands found at 457 and 472 cm−1 are assigned to the (AsO4)3− ν2 bending modes. A comparison is made with the previously obtained spectral data on the discredited mineral clinotyrolite. Copyright © 2015 John Wiley & Sons, Ltd.