The evidence of hydrated proton in eudialyte-group minerals based on Raman spectroscopy data

Hydronium (oxonium) cation H3O+ plays an important role in mineralogy and mineral structures. However, it is rather difficult to detect it using conventional methods of crystal structure analysis. In particular, hydronium-bearing eudialyte-group minerals (EGMs) are well known. In this paper, we provide data on a low-temperature X-ray structure analysis and vibrationl spectroscopy study of previously described potassium-oxonium eudialyte from the Khibiny alkaline massif (Kola Peninsula, Russia) as well as new data on vibrational spectra and hydrogen bonding of a series of sodium-deficient hydrated EGMs including new samples and minerals whose crystal structures were investigated earlier. Based on single-crystal X-ray structural analysis and Raman spectroscopy, it is shown that natural sodium-deficient hydrated zirconosilicates related to eudialyte contain different hydrated proton complexes with extremely strong hydrogen bonds. The data obtained have been compared with recent high-level quantum electronic and vibrational calculations. Some hydrated proton complexes in hydrated eudialyte-related minerals have Zundel- and Eigen-type configurations with the (OO)-O-center dot center dot center dot distances of similar to 2.40 and similar to 2.55 angstrom, respectively.

Automated summary

This paper focuses on the importance of hydronium (oxonium) cation H3O+ in mineralogy and mineral structures. It provides data on a low-temperature X-ray structure analysis and vibrational spectroscopy study of potassium-oxonium eudialyte and a series of sodium-deficient hydrated EGMs. The results show that these minerals contain hydrated proton complexes with extremely strong hydrogen bonds.