A note on the Raman spectra of water-bearing albite glasses     

Paul F. McMillan  Sigurdur Jakobsson  John R. Holloway  Lynn A. Silver 《Geochimica et cosmochimica acta》1983,47(11):1937-1943

The Raman spectra of albite glasses with 4.5 and 6.6 weight percent water have been obtained, and are compared with that of a dry sample. The hydrous glasses show bands near 3600 cm^?1 due to O-H stretching, and a previously unreported weak band near 1600 cm^?1 due to bending of molecular H₂O. Other weak spectral features are discussed, and the effect of dissolved water on the aluminosilicate framework vibrations is considered.  相似文献   

Empirical study of the infrared lattice vibrations (1100–350 cm−1) of phlogopite     

David M. Jenkins 《Physics and Chemistry of Minerals》1989,16(4):408-414

A detailed evaluation of the assignments given to the infrared (IR) vibrations in the lattice stretching region is presented here based on observations of the effects of various chemical substitutions in synthetic analogues of phlogopite, KMg₃(AlSi₃)O₁₀(OH)₂. As in previous studies, this study has confirmed that the 995, 960, and 460 cm^?1 vibrations are influenced by Si, the 822 and 760 cm^?1 vibrations by Al, the 915 and 725 cm^?1 vibrations by Al and Si, and the 592 cm^?1 vibration by OH. Contrary to previous studies, it is shown here that the 690, 495, and 375 cm^?1 vibrations are strongly linked with Mg and not just Si. The 655 cm^?1 band in phlogopite is attributed to an in-plane Al-O vibration rather than an Al-O-Si vibration. As a check on the band assignments made here, IR spectra were obtained for synthetic clintonite, CaMg₂Al(Al₃Si)O₁₀(OH)₂, as well as its chemical analogues and compared with the IR spectrum of phlogopite. The band intensities for the Si-O, Al-O, and Si-O-Mg vibrations changed in accord with the composition of clintonite. The most intense band in clintonite at 660 cm^?1 appears to be associated only with Al and is assigned here to a tetrahedral Al-O-Al vibration which must be present, if not dominant, in this mineral. The near coincidence of an in-plane Al-O vibration at 655 cm^?1 (phlogopite) and an in-plane Al-O-Al vibration at 660 cm^?1 (clintonite) makes the identification of tetrahedral Al-Si order-disorder in trioctahedral layered silicates by IR spectroscopy very difficult. The ratio of the 822/995 cm^?1 bands may, however, prove to be very useful for discerning the amount of tetrahedrally coordinated Al in these types of minerals.  相似文献   

Low-temperature evolution of OH bands in synthetic forsterite, implication for the nature of H defects at high pressure   总被引：1，自引：1，他引：0  

J. Ingrin  J. Liu  C. Depecker  S. C. Kohn  E. Balan  K. J. Grant 《Physics and Chemistry of Minerals》2013,40(6):499-510

We performed in situ infrared spectroscopic measurements of OH bands in a forsterite single crystal between ?194 and 200 °C. The crystal was synthesized at 2 GPa from a cooling experiment performed between 1,400 and 1,275 °C at a rate of 1 °C per hour under high silica-activity conditions. Twenty-four individual bands were identified at low temperature. Three different groups can be distinguished: (1) Most of the OH bands between 3,300 and 3,650 cm^?1 display a small frequency lowering (<4 cm^?1) and a moderate broadening (<10 cm^?1) as temperature is increased from ?194 to 200 °C. The behaviour of these bands is compatible with weakly H-bonded OH groups associated with hydrogen substitution into silicon tetrahedra; (2) In the same frequency range, two bands at 3,617 and 3,566 cm^?1 display a significantly anharmonic behaviour with stronger frequency lowering (42 and 27 cm^?1 respectively) and broadening (~30 cm^?1) with increasing temperature. It is tentatively proposed that the defects responsible for these OH bands correspond to H atoms in interstitial position; (3) In the frequency region between 3,300 and 3,000 cm^?1, three broad bands are identified at 3,151, 3,178 and 3,217 cm^?1, at ?194 °C. They exhibit significant frequency increase (~20 cm^?1) and broadening (~70 cm^?1) with increasing temperature, indicating moderate H bonding. These bands are compatible with (2H)_Mg defects. A survey of published spectra of forsterite samples synthesized above 5 GPa shows that about 75 % of the incorporated hydrogen belongs to type (1) OH bands associated with Si substitution and 25 % to the broad band at 3,566 cm^?1 (type (2); 3,550 cm^?1 at room temperature). The contribution of OH bands of type (3), associated to (2H)_Mg defects, is negligible. Therefore, solubility of hydrogen in forsterite (and natural olivine compositions) cannot be described by a single solubility law, but by the combination of at least two laws, with different activation volumes and water fugacity exponents.  相似文献   

Electronic absorption spectra of chromium-bearing sapphirine     

K. Langer  A. N. Platonov  S. S. Matsuk  M. Andrut 《Physics and Chemistry of Minerals》1994,21(1-2):29-35

Violet, non-pleochroic and greenish-blue, pleochroic chromium-substituted sapphirines were found in corundum-bearing spinel-websterite xenolites from the Yakutian kimberlite pipes Noyabrskaya (N) and Sludyanka (Sl), respectively. The crystallochemical formulae of sapphirine crystals from such xenolites were determined by EMP to be (Mg_3.40Fe_0.23Al_3.25Cr_0.16)^[6] Al _1.00 ^[6] [O₂/Al_4.53Si_1.47O₁₈] (N) and (Mg_2.53Fe_0.55 Mn_0.04Ti _0.03 ⁴⁺ Al_3.55Cr _0.08 ³⁺ )^[6]Al _1.00 ^[16] [O₂/Al_4.28Si_1.73O₁₈] (Sl). Single crystal spectra in the range 35000–6000 cm^1- showed a slightly polarization dependent absorption edge near 3200 cm^1- (N) or 30000 cm^1- (Sl) and unpolarized bands at 25300 and 17300 cm^1-, typical of spin-allowed transitions, derived from ⁴A_2g→⁴T_1g and ⁴A_2g→⁴T_2g, of Cr³⁺ in octahedral sites, with point symmetry C₁, of the structure. Another weak band at 23000 cm^?1 in the sapphirine-N spectra is attributed to low symmetry splitting of the excited ⁴T₁ (F)-State of Cr³⁺. These assignments lead to crystal field parameters Dq=1730cm^?1 and B= 685cm^?1 of Cr³⁺ in sapphirine. Crystallochemical and spectroscopic arguments suggest that Cr³⁺ subsitutes for Al in the M(1) or M(8) sites of the sapphirine structure. In addition to Cr³⁺-transitions, spectra of Sl exhibit weak dd-bands of Fe²⁺ at 10000 and 7700 cm^1-, which are unpolarized in consistency with the C₁ site symmetry of the octahedra in the structure. Spectra of Sl show also prominent, broad bands (Δv_1/2～-5000 cm^1-) at 15000 and 11000 cm^1-, which occur in E//Y(//b) and E//Z(//_c=12°) only and exhibit an intensity ratio α_Y∶α_z close to 1∶3. This result, the large half width, as well as band energy — MM distance considerations suggest that these bands originate from Fe^2+[6]-Fe^3+[6] charge-transfer transitions in wall octahedra M(1)M(2), M(6)M(7) etc., forming MM vectors of 30° with the c-axis. The lack of Fe²⁺-Fe³⁺ charge-transfer bands in sapphirine N might indicate a lower oxygen fugacity during the formation of the websterite from the Noyabrskaya pipe compared to that from the Sludyanka pipe.  相似文献   

On the mechanisms for H and Al incorporation in stishovite     

Geoffrey D. Bromiley  Fiona A. Bromiley  David W. Bromiley 《Physics and Chemistry of Minerals》2006,33(8-9):613-621

The solubility and incorporation mechanisms of hydrogen in synthetic stishovite as a function of Al₂O₃ content have been investigated. Mechanisms for H incorporation in stishovite are more complex than previously thought. Most H in stishovite is incorporated via the Smyth et al. (Am Mineral 80:454–456, 1995) model, where H docks close to one of the shared O–O edges, giving rise to an OH stretching band in infrared (IR) spectra at 3,111–3,117 cm⁻¹. However, careful examination of IR spectra from Al-stishovite reveals the presence of an additional OH band at 3,157–3,170 cm⁻¹. All H is present on one site, with interstitial H both coupled to Al³⁺ substitutional defects on adjacent octahedral (Si⁴⁺) sites, and decoupled from other defects, giving rise to two distinct absorption bands. Trends in IR data as a function of composition are consistent with a change in Al incorporation mechanism in stishovite, with Al³⁺ substitution for Si⁴⁺ charge-balanced by oxygen vacancies at low bulk Al₂O₃ contents, and coupled substitution of Al³⁺ onto octahedral (Si⁴⁺) and interstitial sites at high bulk Al₂O₃ contents. Trends in OH stretching frequencies as a function of Al₂O₃ content suggest that any such change in Al incorporation mechanism could alter the effect that Al incorporation has on the compressibility of stishovite, as noted by Ono et al. (Am Mineral 87:1486–1489, 2002).  相似文献   

Crystal chemistry of tremolite–tschermakite solid solutions     

J. Najorka  M. Gottschalk 《Physics and Chemistry of Minerals》2003,30(2):108-124

Tremolite–tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide–hydroxide mixtures and an additional 0.1–1.8 molal CaBr₂ solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al tremolites were solid solutions in the ternary tremolite–tschermakite–cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (X_ts=0.54). Different cummingtonite concentrations (X_cum=0.00–0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) Å, b=17.936(14) Å, c=5.2995(3) Å, β=105.68(9)° and V=891.7 ± 1.4 ų were extrapolated by least-squares regression. Using the a and β lattice parameters for tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664–3676 cm^?1 (I), 3633–3664 cm^?1 (II) and 3526–3633 cm^?1 (III). Assuming ^[6]Al substitution at M2 and/or M3 and ^[4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si⁴⁺ at T1 and one or two Al³⁺ at M2 and/or M3_far, II: one Al³⁺ at T1 and one to three Al³⁺ at M2 and/or at M3_far, III: either Al³⁺ on M3_near and/or two Al³⁺ on T1 and additional one to four Al³⁺ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results.  相似文献   

Combined inelastic neutron scattering and solid-state DFT study of dynamics of hydrogen atoms in trioctahedral 1M phlogopite     

L’ubomír Smr?ok  Alexander I. Kolesnikov  Milan Rieder 《Physics and Chemistry of Minerals》2012,39(9):779-787

Inelastic neutron scattering (INS) was used to study the vibrational dynamics of the hydrogen atoms in natural trioctahedral phlogopite, K_0.93Na_0.03(Mg_2.47Fe_0.22Al_0.16Fe_0.04Tl_0.06)[Si_2.84Al_1.16]O₁₀OH_1.71F_0.28Cl_0.01, within the 50–1,000?cm^?1 energy range. The INS spectra collected using direct geometry spectrometer SEQUOIA (ORNL) were interpreted by means of the solid-state DFT calculations covering both normal mode analysis and molecular dynamics. To optimize the structure and to calculate the vibrational modes under harmonic approximation, both a hybrid PBE0 and the AM05 functional were used, while the molecular dynamics calculations (60?ps/1?fs) were performed only with the computationally less-demanding AM05 functional. The main contributions to the dominant band within ~750–550?cm^?1 are symmetric and antisymmetric Mg–O–H bending modes, overlapping with the skeletal stretching and bending modes causing weaker secondary movements of H atoms of inner hydroxyl groups. Signatures of the Mg–O–H bending modes appear down to ~400?cm^?1, where a region of octahedra deformation modes starts. These deformations cause just shallow movements of the hydrogen atoms and are mirrored by the modes with close vibrational energies. The region from ~330?cm^?1 down to the low-energy end of the spectrum portrays induced vibrations of the H atoms caused by deformation of individual polyhedra, translational vibrations of the parts of the 2:1 layer relative one to another, and librational and translational vibrations of the layer. The main difference between the INS spectrum of dioctahedral Al-muscovite and trioctahedral Mg-phlogopite is that the Mg–O–H modes are all assigned to in-plane vibrations of the respective hydrogen atoms.  相似文献   

Dehydration experiments on natural omphacites: qualitative and quantitative characterization by various spectroscopic methods   总被引：1，自引：0，他引：1  

M. Koch-Müller  I. Abs-Wurmbach  D. Rhede  V. Kahlenberg  S. Matsyuk 《Physics and Chemistry of Minerals》2007,34(9):663-678

A series of natural omphacites from a wide range of P, T occurrences were investigated by electron microprobe (EMP), infrared (IR)-, Mössbauer (MS)- and optical spectroscopy in the UV/VIS spectral range (UV/VIS), secondary ion mass spectrometry (SIMS) and single crystal structure refinement by X-ray diffraction (XRD) to study the influence of hydrogen loss on valence state and site occupancies of iron. In accordance with literature data we found Fe²⁺ at M1 as well as at M2, and in a first approach assigned Fe³⁺ to M1, as indicated by MS and XRD results. Hydrogen content of three of our omphacite samples were measured by SIMS. In combination with IR spectroscopy we determined an absorption coefficient: ε _i,tot = 65,000 ± 3,000 lmol_H2O ^?1 cm^?2. Using this new ε _i,tot value, we obtained water concentrations ranging from 60 to 700 ppm H₂O (by weight). Hydrogen loss was simulated by stepwise heating the most water rich samples in air up to 800°C. After heat treatment the samples were analyzed again by IR, MS, UV/VIS, and XRD. Depending on the type of the OH defect, the grade of dehydration with increasing temperature is significantly different. In samples relatively poor in Fe³⁺ (<0.1 Fe³⁺ pfu), hydrogen associated with vacancies at M2 (OH bands around 3,450 cm^?1) starts to leave the structure at about 550°C and is completely gone at 780°C. Hydrogen associated with Al³⁺ at the tetrahedral site (OH bands around 3,525 cm^?1, Koch-Müller et al., Am Mineral, 89:921–931, 2004) remains completely unaffected by heat treatment up to 700°C. But all hydrogen vanished at about 775°C. However, this is different for a more Fe³⁺-rich sample (0.2 Fe³⁺ pfu). Its IR spectrum is characterized by a very intense OH band at 3,515 cm^?1 plus shoulder at 3,450 cm^?1. We assign this intense high-energy band to vibrations of an OH dipole associated with Fe³⁺ at M1 and a vacancy either at M1 or M2. OH release during heating is positively correlated with decrease in Fe²⁺ and combined with increase in Fe³⁺. That dehydration is correlated with oxidation of Fe²⁺ is indirectly confirmed by annealing of one sample in a gas mixing furnace at 700°C under reducing conditions keeping almost constant OH^? content and giving no indication of Fe²⁺-oxidation. Obtained data indicate that in samples with a relatively high concentration of Fe²⁺ at M2 and low-water concentrations, i.e., at a ratio of Fe^{2+ M2}/H > 10 dehydration occurs by iron oxidation of Fe²⁺ exclusively at the M2 site following the reaction: \( {\left[ {{\text{Fe}}^{{{\text{2 + [ M2]}}}}{\text{OH}}^{ - } } \right]} = {\left[ {{\text{Fe}}^{{{\text{3 + [ M2]}}}} {\text{O}}^{{{\text{2}} - }} } \right]} + {\text{1/2}}\;{\text{H}}_{{\text{2}}} \uparrow . \) In samples having relatively low concentration of Fe²⁺ at M2 but high-water concentrations, i.e., ratio of Fe^{2+ M2}/H < 5.0 dehydration occurs through oxidation of Fe²⁺ at M1.  相似文献   

Diffusion and solubility of hydrogen and water in periclase     

Bastian Joachim  Anke Wohlers  Nicholas Norberg  Emmanuel Gardés  Elena Petrishcheva  Rainer Abart 《Physics and Chemistry of Minerals》2013,40(1):19-27

Cylinders of synthetic periclase single crystals were annealed at 0.15–0.5 GPa and 900–1200 °C under water-saturated conditions for 45 min to 72 h. Infrared spectra measured on the quenched products show bands at 3,297 and 3,312 cm^?1 indicating V _OH ^? centers (OH-defect stretching vibrations in a half-compensated cation vacancy) in the MgO structure as a result of proton diffusion into the crystal. For completely equilibrated specimens, the OH-defect concentration, expressed as H₂O equivalent, was calculated to 3.5 wt ppm H₂O at 1,200 °C and 0.5 GPa based on the calibration method of Libowitzky and Rossmann (Am Min 82:1111–1115, 1997). This value was confirmed via Raman spectroscopy, which shows OH-defect-related bands at identical wavenumbers and yields an H₂O equivalent concentration of about 9 wt ppm using the quantification scheme of Thomas et al. (Am Min 93:1550–1557, 2008), revised by Mrosko et al. (Am Mineral 96:1748–1759, 2011). Results of both independent methods give an overall OH-defect concentration range of 3.5–9 (+4.5/?2.6) ppm H₂O. Proton diffusion follows an Arrhenius law with an activation energy E _a = 280 ± 64 kJ mol^?1 and the logarithm of the pre-exponential factor logD_o (m² s^?1) = ?2.4 ± 1.9. IR spectra taken close to the rims of MgO crystals that were exposed to water-saturated conditions at 1,200 °C and 0.5 GPa for 24 h show an additional band at 3,697 cm^?1, which is related to brucite precipitates. This may be explained by diffusion of molecular water into the periclase, and its reaction with the host crystal during quenching. Diffusion of molecular water may be described by logD_H2O (m² s^?1) = ?14.1 ± 0.4 (2σ) at 1,200 °C and 0.5 GPa, which is ~ 2 orders of magnitude slower than proton diffusion at identical P-T conditions.  相似文献   

A single-crystal neutron and X-ray diffraction study of pezzottaite, Cs(Be2Li)Al2Si6O18     

G. Diego Gatta  Ilaria Adamo  Martin Meven  Erica Lambruschi 《Physics and Chemistry of Minerals》2012,39(10):829-840

The chemical composition and the crystal structure of pezzottaite [ideal composition Cs(Be₂Li)Al₂Si₆O₁₈; space group: ${\it{R}} \overline{\text{3}} $ c, a?=?15.9615(6) ?, c?=?27.8568(9) ?] from the type locality in Ambatovita (central Madagascar) were investigated by electron microprobe analysis in wavelength dispersive mode, thermo-gravimetric analysis, Fourier-transform infrared spectroscopy, single-crystal X-ray (at 298?K) and neutron (at 2.3?K) diffraction. The average chemical formula of the sample of pezzottaite resulted ^Cs1,Cs2(Cs_0.565Rb_0.027K_0.017)_Σ0.600 ^Na1,Na2(Na_0.101Ca_0.024)_Σ0.125Be_2.078Li_0.922 ^Al1,Al2(Mg_0.002Mn_0.002Fe_0.003Al_1.978)_Σ1.985 ^Si1,Si2,Si3(Al_0.056Si_5.944)_Σ6O₁₈·0.27H₂O. The (unpolarized) IR spectrum over the region 3,800–600?cm^?1 was collected and a comparison with the absorption bands found in beryl carried out. In particular, two-weak absorption bands ascribable to the fundamental H₂O stretching vibrations (i.e. 3,591 and 3,545?cm^?1) were observed, despite the mineral being nominally anhydrous. The X-ray and neutron structure refinements showed: (a) a non-significant presence of aluminium, beryllium or lithium at the Si1, Si2 and Si3 sites, (b) the absence (at a significant level) of lithium at the octahedral Al1, Al2 and Al3 sites and (c) a partial lithium/beryllium disordering between tetrahedral Be and Li sites.  相似文献   

The crystal chemistry of birefringent natural uvarovites. Part III. Application of the superposition model of crystal fields with a characterization of synthetic cubic uvarovite     

M. Andrut  M. Wildner 《Physics and Chemistry of Minerals》2002,29(9):595-608

Synthetic, flux-grown uvarovite, Ca₃Cr₂ [SiO₄]₃, was investigated by optical methods, electron microprobe analysis, UV-VIS-IR microspectrometry, and luminescence spectroscopy. The crystal structure was refined using single-crystal X-ray CCD diffraction data. Synthetic uvarovite is optically isotropic and crystallizes in the “usual” cubic garnet space group Ia3¯d [a=11.9973 Å, Z=8; 21524 reflections, R1=2.31% for 454 unique data and 18 variables; Cr–O=1.9942(6), Si–O=1.6447(6), Ca–O_a=2.3504(6), Ca–O_b= 2.4971(6) Å]. The structure of Ca₃Cr₂[SiO₄]₃ complies with crystal-chemical expectations for ugrandite group garnets in general as well as with predictions drawn from “cubically averaged” data of non-cubic uvarovite–grossular solid solutions (Wildner and Andrut 2001). The electronic absorption spectra of Cr³⁺ in trigonally distorted octahedra of synthetic uvarovite were analyzed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsion parameters are =9532 cm^?1, =4650 cm^?1, power law exponent t ₄=6.7, Racah B₃₅=703 cm^?1 at 290 K (reference distance R ₀=1.995 Å; fixed power law exponent t ₂=3 and spin-orbit parameter ζ=135 cm^?1). The interelectronic repulsion parameters Racah B ₅₅=714 cm^?1 and C=3165 cm^?1 were extracted from spin-forbidden transitions. This set of SM parameters was subsequently applied to previously well-characterized natural uvarovite–grossular solid solutions (Andrut and Wildner 2001a; Wildner and Andrut 2001) using their extrapolated Cr–O bond lengths to calculate the energies of the spin-allowed bands. These results are in very good agreement with the experimentally determined band positions and indicate the applicability of the superposition model to natural 3d ^N prevailing systems in geosciences. Single-crystal IR absorption spectra of synthetic uvarovite in the region of the OH-stretching vibration exhibit one isotropic absorption band at 3508 cm^?1 at ambient conditions, which shifts to 3510 cm^?1 at 77 K. This band is caused by structurally incorporated hydroxyl groups via the (O₄H₄)-hydrogarnet substitution. The water content, calculated using an integral extinction coefficient ?=60417 cm^?2 l mol^?1, is c _H2O=33 ppm.  相似文献   

Intercalation of kaolinite with acetamide     

R. L. Frost  J. Kristof  G. N. Paroz  J. T. Kloprogge 《Physics and Chemistry of Minerals》1999,26(3):257-263

Upon intercalation of both ordered (low defect) and disordered (high defect) kaolinites with acetamide, two types of interaction are observed. Firstly, hydrogen bonding between the NH₂ groups of the acetamide with the siloxane oxygens is formed, as evidenced by the formation of two new bands at 3400 and 3509 cm^–1. Secondly, the appearance of additional bands at ∼3600 cm^–1 in both the infrared and Raman spectra of the acetamide intercalates is attributed to a second type of hydrogen bonding by the interaction of the C=O group and the inner surface hydroxyls. Changes in the intensity of the hydroxyl deformation modes in the 895 to 940 cm^–1 region are attributed to the changes in the hydrogen bonding of the kaolinite surfaces. It is proposed that the hydrogen bonding between the adjacent kaolinite layers is replaced with hydrogen bonding between both kaolinite surfaces and the acetamide molecule. Changes in the molecular structure of acetamide are observed upon intercalation. The amide 1 band is lost and replaced with a well-defined NH₂ deformation vibration. The loss of the amide 1 band is attributed the hydrogen bond formation between the amide hydrogens and the siloxane surface. The bands of the C=O group at 1680 and 1740 cm^–1 become a single band at 1680 cm^–1. The amide 2 band remains unchanged. The lack of intensity of the 1740 cm^–1 band is attributed to the formation of hydrogen bonding between the inner surface hydroxyl groups and the carbonyl group. Received: 4 February 1998/ Revised, accepted: 30 June 1998  相似文献   

Temperature dependence of Raman spectra of the quartz- and rutile-types of GeO2     

Terrence P. Mernagh  Lin-gun Liu 《Physics and Chemistry of Minerals》1997,24(1):7-16

The temperature dependence (at ambient pressure) of the Raman spectra of both the quartz- and rutile-types of GeO₂ has been studied from 109 to 874?K. All spectra were corrected for the effects of temperature and are presented in their reduced form to allow a direct comparison of intensities at all temperatures. In the quartz-type GeO₂, the Raman bands above 400?cm^?1 exhibited relatively larger temperature dependences and at least four of the bands in this region vary nonlinearly with increasing temperature. Deconvolution of the most intense Raman band at 700?cm^?1 in the rutile-type GeO₂ revealed the presence of a previously unreported band at 684?cm^?1 at 298?K which may arise from splitting of the A_1g mode. A nonlinear temperature dependence was observed for all the Raman bands above 600?cm^?1 in the rutile-type GeO₂ with the new band at 684?cm^?1 exhibiting the largest curvature. In common with previous studies of rutile-type oxides, the B_1g mode at 171?cm^?1 showed anomalous behaviour by increasing linearly in frequency with increasing temperature. In a separate experiment, the oxidation of metallic germanium in air demonstrated that the quartz-type GeO₂ is the preferred form of germanium oxide at temperatures above 745?K at atmospheric pressure. Thermodynamic calculations predict that the rutile-form of GeO₂ should be the stable species under these conditions. This suggests that atmospheric gases may have a marked effect on the kinetics and stability of the quartz and rutile forms of GeO₂.  相似文献   

Mechanisms of OH defect incorporation in naturally occurring,hydrothermally formed diopside and jadeite     

M. Andrut  M. Wildner  J. Ingrin  A. Beran 《Physics and Chemistry of Minerals》2007,34(8):543-549

The IR spectrum of an alpine, hydrothermally formed diopside containing 17 wt ppm H₂O consists of three main OH absorption bands centred at 3647, 3464 and 3359 cm⁻¹. Jadeite from a Californian vein occurrence is characterised by bands at 3616 and 3557 cm⁻¹ and contains about 197 wt ppm H₂O. Based on the pleochroic scheme of the OH absorption bands in diopside, OH defect incorporation models are derived on the basis of fully occupied cation sites and under the assumption of M1 and M2 site vacancies; OH defects replacing O2 oxygen atoms are most common. The less pronounced OH pleochroism and the broad band absorption pattern of jadeite indicate a high degree of OH defect disordering. The pleochroic scheme of the main absorption bands at 3616 and 3557 cm⁻¹ implies partial replacement of O2 oxygen atoms by OH dipoles pointing to vacant Si sites. Under the assumption of M1 and M2 site vacancies, O1–H and O2–H defects are also derivable. OH incorporation modes assuming Si-vacancies should be considered for jadeite-rich clinopyroxenes formed in deep crust and upper mantle regions.  相似文献   

Variation of infrared absorption spectra in the system Bi2Al4−x Fe x O9 (x = 0–4), structurally related to mullite     

D. Voll  A. Beran  H. Schneider 《Physics and Chemistry of Minerals》2006,33(8-9):623-628

The crystal structure of Bi₂Al_4−x Fe _x O₉ compounds (x = 0–4) has striking similarities with the crystal structure of mullite. A complete substitution of Al by Fe³⁺ in both octahedral and tetrahedral sites is a particular structural feature. The infrared (IR) spectra of the Bi₂M₄O₉ compounds (M = Al, Fe³⁺) are characterised by three band groups with band maxima in the 900–800, 800–600 and 600–400 cm⁻¹ region. Based on the spectroscopic results obtained from mullite-type phases, the present study focuses on the composition-dependent analysis of the 900–800 cm⁻¹ band group, which is assigned to Al(Fe³⁺)–O stretching vibrations of the corner-sharing MO₄ tetrahedra. The Bi₂Al₄O₉ and Bi₂Fe₄O₉ endmembers display single bands with maxima centred at 922 and 812 cm⁻¹, respectively. Intermediate Bi₂Al_4−x Fe _x O₉ compounds exhibit a distinct splitting into three relatively sharp bands, which is interpreted in terms of ordering effects within the tetrahedral pairs. Thereby the high-energy component band of the band triplet relates to Al–O–Al conjunctions and the low-energy component band to Fe–O–Fe conjunctions. The intermediate band is assigned to stretching vibrations of Al–O–Fe or Fe–O–Al configurations of the corner-sharing tetrahedral pairs. Bands in the 800–600 cm⁻¹ range are assigned to low-energy stretching vibrations of the MO₄ tetrahedra and to M–O–M bending vibrations of the tetrahedral pairs. Absorptions in the 600–400 cm⁻¹ range are essentially determined by M–O stretching modes of the M cations in octahedral coordination.  相似文献   

High temperature infrared spectra of hydrous microcrystalline quartz   总被引：1，自引：0，他引：1  

Hiraku Yamagishi  Satoru Nakashima  Yuki Ito 《Physics and Chemistry of Minerals》1997,24(1):66-74

A series of in-situ high temperature infrared (IR) measurements of water in an agate sample and in a milky quartz has been conducted in order to understand the nature of water in silica at high temperatures (50–700?°C) and the dehydration behavior. IR absorption bands of water molecules trapped in the milky quartz showed a systematic decrease in intensities and a shift from 3425?cm^?1 at 50?°C toward 3590?cm^?1 at 700?°C without any loss of water. This indicates a change in IR absorption coefficients corresponding to different polymeric states of water at different temperatures. The broad 3430?cm^?1 band in the agate sample also showed a systematic decrease in IR intensity and a band shift toward higher frequency with increasing temperature (～700?°C). This indicates that the agate sample also contains fluid inclusion-like water. For this agate sample, a dehydration of loosely hydrogen-bonded molecular water occurred at lower temperatures (<200?°C). At higher temperatures (>400?°C), sharp bands around 3660 and 3725?cm^?1 (3740?cm^?1 at 50?°C) due to surface silanols, appeared. This indicates dehydration of H₂O molecules that are hydrogen bonded to surface silanols. SiOH species in the agate are divided into three groups, namely SiOH group located at structural defects, surface silanols hydrogen bonded to each other and free surface silanols. Former two dehydrate below 700?°C and the dehydration rate of the SiOH at structural defects is faster than the other. IR spectra show that SiOH species decrease continuously even after the dehydration of most of H₂O molecules. All these results provide realistic bases for the change in physicochemical states of different OH species in silica at high temperatures.  相似文献   

Spectroscopic active IVFe3+–VIFe3+ clusters in spinel–magnesioferrite solid solution crystals: a potential monitor for ordering in oxide spinels     

G. B. Andreozzi  U. Hålenius  H. Skogby 《Physics and Chemistry of Minerals》2001,28(7):435-444

Optical absorption spectra (OAS) of synthetic single crystals of the solid solution spinel sensu stricto (s.s.)–magnesioferrite, Mg(Fe³⁺Al_1???y)₂O₄ (0?y?≤ 0.3), have been measured between 12 500 and 28 500?cm^?1. Chemical composition and Fe³⁺ site distribution have been measured by electron microprobe and Mössbauer spectroscopy, respectively. Ferric iron is ordered to the tetrahedral site for samples with small magnesioferrite component, and this ordering is shown to increase with magnesioferrite component. The optical absorption spectra show a strong increase in band intensities with Fe³⁺→Al substitution. Prominent and relatively sharp absorption bands are observed at 25 300 and 21 300?cm^?1, while less intense bands occur at 22 350, 18 900, 17 900 and 15 100?cm^?1. On the basis of band energies, band intensities and the compositional effect on band intensity, as well as structural considerations, we assign the observed bands to electronic transitions in ^IVFe³⁺–^VIFe³⁺clusters. A linear relationship (R ²= 0.99) between the α_net value of the absorption band at 21 300?cm^?1 and [^IVFe³⁺]?·?[^VIFe³⁺] concentration product has been defined: α_net=2.2?+?15.8 [^IVFe³⁺]?·?[^VIFe³⁺]. Some of the samples have been heat-treated between 700 and 1000?°C to investigate the relation between Fe³⁺ ordering and absorption spectra. Increase of cation disorder with temperature is observed, which corresponds to a 4% reduction in the number of active clusters. Due to the high spatial resolution (??～?10?μm), the OAS technique may be used as a microprobe for determination of Fe³⁺ concentration or site partitioning. Potential applications of the technique include analysis of small crystals and of samples showing zonation with respect to total Fe³⁺ and/or ordering.  相似文献   

OH defects in quartz in the system quartz–albite–water and granite–water between 5 and 25?kbar     

Roland Stalder  Jürgen Konzett 《Physics and Chemistry of Minerals》2012,39(10):817-827

The incorporation of OH defects in quartz from the systems quartz–water, quartz–albite–water and granite–water at pressures between 5 and 25?kbar and temperatures between 800 and 1,000?°C was investigated by IR spectroscopy. The two most important OH absorption features can be assigned to hydrogarnet defects (absorption band at 3,585?cm^?1) and coupled substitutions involving Al³⁺ (Al–H defects, absorption bands at 3,310, 3,378 and 3,430?cm^?1). Al incorporation in quartz is controlled by mineral/melt partitioning (D _Al ^Qz/Melt ?=?0.01) and exhibits a negative pressure dependence. This trend is not clearly reflected by the concentration of Al–H defects, which shows positive deviations from the theoretical 1:1 correlation of Al/H for some samples. In contrast to the Al–H defects, formation of hydrogarnet defects appears to be positively correlated to pressure and water activity, and may be used a petrological indicator. The overall water concentration exhibits only minor changes with pressure and temperature, but a clear correlation of water activity (controlled by various amounts of dissolved salts) and hydrogarnet substitution could be established.  相似文献   

Electronic absorption by Ti3+ ions and electron delocalization in synthetic blue rutile     

V. M. Khomenko  K. Langer  H. Rager  A. Fett 《Physics and Chemistry of Minerals》1998,25(5):338-346

Polarized absorption spectra, σ and π, in the spectral range 30000–400 cm⁻¹ (3.71–0.05 eV) were obtained on crystal slabs // [001] of deep blue rutile at various temperatures from 88 to 773 K. The rutile crystals were grown in Pt-capsules from carefully dried 99.999% TiO₂ rutile powder at 50 kbar/1500 °C using graphite heating cells in a belt-type apparatus. Impurities were below the detection limits of the electron microprobe (about 0.005 wt% for elements with Z≥13). The spectra are characterized by an unpolarized absorption edge at 24300 cm⁻¹, two weak and relatively narrow (Δν_1/2≈3500–4000 cm⁻¹), slightly σ-polarized bands ν₁ at 23500 cm⁻¹ and ν₂ at 18500 cm⁻¹, and a complex, strong band system in the NIR (near infra red) with sharp weak peaks in the region of the OH stretching fundamentals superimposed on the NIR system in the σ-spectra. The NIR band system and the UV edge produce an absorption minimum in both spectra, σ and π, at 21000 cm⁻¹, i.e. in the blue, which explains the colour of the crystals. Bands ν₁ and ν₂ are assigned to dd transitions to the Jahn-Teller split upper E_g state of octahedral Ti³⁺. The NIR band system can be fitted as a sum of three components. Two of them are partly π-polarized, nearly Gaussian bands, both with large half widths 6000–7000 cm⁻¹, ν₃ at 12000 cm^–1 and the most intense ν₄ at 6500 cm⁻¹. The third NIR band ν₅ of a mixed Lorentz-Gaussian shape with a maximum at 3000 cm⁻¹ forms a shoulder on the low-energy wing of ν₄. Energy positions, half band widths and temperature behaviour of these bands are consistent with a small polaron type of Ti³⁺Ti⁴⁺ charge transfer (CT). Polarization dependence of CT bands can be explained on the basis of the structural model of defect rutile by Bursill and Blanchin (1983) involving interstitial titanium. Two OH bands at 3322 and 3279 cm⁻¹ in σ-spectra show different stability during annealing, indicating two different positions of proton in the rutile structure, one of them probably connected with Ti³⁺ impurity. Total water concentration in blue rutile determined by IR spectroscopy is 0.10 wt-% OH. The EPR spectra measured in the temperature interval 20–295 K show the presence of an electron centre at temperatures above 100 K and Ti³⁺ ions in more than one structural position, but predominantly in compressed interstitial octahedral sites, at lower temperatures. These results are in good agreement with the conclusions based on the electronic absorption data. Received: 24 March 1997 / Revised, accepted: 14 October 1997  相似文献   

Low temperature spectral studies of Mn3+-bearing andalusite and epidote type minerals in the range 30000–5000 cm−1     

Smith  G.  Hålenius  U.  Langer  K. 《Physics and Chemistry of Minerals》1982,8(3):136-142

Polarized absorption spectra of natural piemontite (Ca_1.802Mn ²⁺_0.178 Mg_0.025) (Mn ³⁺_0.829 Fe ³⁺_0.346 Al_1.825) [(Si_2.992Al_0.008) O₁₂OH], viridine (Al_1.945Mn ³⁺_0.033 Fe ³⁺_0.063 Mg_0.003) [O|Si_0.970 O₄], and kanonaite (Al_1.291Mn ³⁺_0.682 Fe ³⁺_0.019 ) [O|Si_1.006 O₄] were measured at 295 and ca. 100 K. For piemontite, lowering the temperature resulted in a sharpening of broad bands in the 10 000–25 000 cm⁻¹ region supporting their assignment to single ion Mn³⁺ in M3 non-centrosymmetric sites.

Alternatively, in kanonaite, temperature behaviour pointed to a slightly stronger influence of vibronic coupling on strong bands near 16 000 and 22 000 cm⁻¹, which supported an interpretation of Mn³⁺ in nearly centrosymmetric M1 sites. Measurements at ca. 100 K show pronounced fine structure in the viridine spectra which is attributed to Fe³⁺. The ɛ values for Mn³⁺ spin-allowed bands in the three minerals lie in the range 18 to 227 [1·g-atom⁻¹·cm⁻¹].

For the same band and polarisation, ɛ values in Mn³⁺-bearing andalusite-type minerals viridine and kanonaite are the same, which indicates an absence of strong magnetic coupling effects between Mn³⁺ ions in the andalusite type structure down to ca. 100 K.

In silicates, the high ɛ values for Mn³⁺ spin-allowed bands, in comparison to those obtained for Fe²⁺ spin-allowed bands from sites of “similar distortion”, is attributed to a higher degree of covalency in the Mn³⁺-O bonds compared to the Fe²⁺-O bonds, as a result of the higher valence state of manganese.

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