Spectroscopic and bond-topological investigation of interstitial volatiles in beryl from Slovakia
| Authors | |
|---|---|
| Year of publication | 2016 |
| Type | Article in Periodical |
| Magazine / Source | Physics and Chemistry of Minerals |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1007/s00269-016-0806-9 |
| Field | Geology and mineralogy |
| Keywords | Beryl; Infrared spectroscopy; Raman spectroscopy; Thermal analysis; Bond topology |
| Description | 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-nu(1); (2) antisymmetric stretching mode-nu(3); (3) bending vibration-nu(2). 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 nu(1) 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 center dot center dot center dot O1 bonds and one Na-O-W 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-O-W bond strength of 0.28 vu and two H center dot center dot center dot O1 bonds of 0.14 vu without any forced angular distortion is the most stable of all. |
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