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791.
Spectroscopic and bond-topological investigation of interstitial volatiles in beryl from Slovakia 总被引:1,自引:0,他引:1
Jana Fridrichová Peter Bačík Valéria Bizovská Eugen Libowitzky Radek Škoda Pavel Uher Daniel Ozdín Martin Števko 《Physics and Chemistry of Minerals》2016,43(6):419-437
Nine beryl samples from Western Carpathians, Slovakia, were investigated by infrared and Raman spectroscopy and differential thermal analysis. Two types of water H2O I and H2O II were detected. Infrared spectroscopy proved the presence of water type I and II in the presence of alkali cations with several bands: (1) symmetric stretching vibration—ν1; (2) antisymmetric stretching mode—ν3; (3) bending vibration—ν2. The presence of singly and doubly coordinated type II water (IIs and IId) was confirmed by single-crystal IR spectroscopy. From Raman spectra a band at 3606 cm?1 was assigned to ν1 of water type I and the range of 3597–3600 cm?1 to water type II. The presence of doubly coordinating water indicates a relatively highly hydrated environment with the presence of alkali ions including Na as the dominant cation coordinated by H2O II. CO2 bands were detected only by single-crystal IR spectroscopy. Thermal analysis proved total water loss in the range of 1.4–2.0 wt% and three main dehydration events. Based on the study of bond-topological arrangements two molecules of H2O IId are each bound with two H···O1 bonds and one Na–OW bond with an angular distortion, and by releasing one H2O molecule more stable H2O IIs is produced. The H2O I molecule is bound only by two equivalent hydrogen bonds. The H2O IIs molecule with a Na–OW bond strength of 0.28 vu and two H···O1 bonds of 0.14 vu without any forced angular distortion is the most stable of all. 相似文献
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G. Diego Gatta Günther J. Redhammer Alessandro Guastoni Giorgio Guastella Martin Meven Alessandro Pavese 《Physics and Chemistry of Minerals》2016,43(5):341-352
The crystal chemistry of a ferroaxinite from Colebrook Hill, Rosebery district, Tasmania, Australia, was investigated by electron microprobe analysis in wavelength-dispersive mode, inductively coupled plasma–atomic emission spectroscopy (ICP–AES), 57Fe Mössbauer spectroscopy and single-crystal neutron diffraction at 293 K. The chemical formula obtained on the basis of the ICP–AES data is the following: \( ^{X1,X2} {\text{Ca}}_{4.03} \,^{Y} \left( {{\text{Mn}}_{0.42} {\text{Mg}}_{0.23} {\text{Fe}}^{2 + }_{1.39} } \right)_{\varSigma 2.04} \,^{Z1,Z2} \left( {{\text{Fe}}^{3 + }_{0.15} {\text{Al}}_{3.55} {\text{Ti}}_{0.12} } \right)_{\varSigma 3.82} \,^{T1,T2,T3,T4} \left( {{\text{Ti}}_{0.03} {\text{Si}}_{7.97} } \right)_{\varSigma 8} \,^{T5} {\text{B}}_{1.96} {\text{O}}_{30} \left( {\text{OH}} \right)_{2.18} \). The 57Fe Mössbauer spectrum shows unambiguously the occurrence of Fe2+ and Fe3+ in octahedral coordination only, with Fe2+/Fe3+ = 9:1. The neutron structure refinement provides a structure model in general agreement with the previous experimental findings: the tetrahedral T1, T2, T3 and T4 sites are fully occupied by Si, whereas the T5 site is fully occupied by B, with no evidence of Si at the T5, or Al or Fe3+ at the T1–T5 sites. The structural and chemical data of this study suggest that the amount of B in ferroaxinite is that expected from the ideal stoichiometry: 2 a.p.f.u. (for 32 O). The atomic distribution among the X1, X2, Y, Z1 and Z2 sites obtained by neutron structure refinement is in good agreement with that based on the ICP–AES data. For the first time, an unambiguous localization of the H site is obtained, which forms a hydroxyl group with the oxygen atom at the O16 site as donor. The H-bonding scheme in axinite structure is now fully described: the O16–H distance (corrected for riding motion effect) is 0.991(1) Å and an asymmetric bifurcated bonding configuration occurs, with O5 and O13 as acceptors [i.e. with O16···O5 = 3.096(1) Å, H···O5 = 2.450(1) Å and O16–H···O5 = 123.9(1)°; O16···O13 = 2.777(1) Å, H···O13 = 1.914(1) Å and O16–H···O13 = 146.9(1)°]. 相似文献
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Miroslav Nastev Michel Parent Nicolas Benoit Martin Ross Danielle Howlett 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(3):200-212
Shear-wave velocity of the top 30?m, VS30, is commonly used for prediction of the seismic site response. This paper presents development, validation and uncertainty assessment of a regional VS30 model based on a combination of simplified 3D geology and statistically representative velocity values. Results identify soft marine sediments in deep sedimentary basins as zones most susceptible to seismic shaking. Compared to the available urban-scale seismic zonation studies, the regional model showed a success rate of roughly 64% in predicting local site category. The standard deviation was in average 30% of the expected VS30 value. 相似文献
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