Rare cyclosilicate odintsovite K2Na4Ca3Ti2Be4Si12O38: new crystal-chemical data

Abstract

The Murun massif (Aldan shield, Russia) is particularly intriguing due to its group of alkali Ca-(K)-(Na) silicates, which includes many new and rare species. Additionally, it is also of interest for its beryllium mineralization. One of the unique beryllium Ca-(K)-(Na) silicates, odintsovite K₂Na₄Ca₃Ti₂Be₄Si₁₂O₃₈, was investigated in this study. The aim of this study is to provide new insights into the crystal chemistry and spectroscopic properties of odintsovite. DFT modelling was used to interpret the experimental IR and Raman spectra. Determining the crystal-chemical formula of odintsovite is challenging due to the presence of atoms in different structural positions with varying valence states. The distribution of cations was determined by combining electron probe microanalysis with the results of crystal structure refinement. Luminescence of Eu³⁺ was observed in odintsovite upon excitation at around 532 nm. Analysis of the luminescence band splitting is related to the 4f–4f transitions in Eu³⁺ ions. Additionally, upon excitation at around 370 nm, luminescence with a peak at around 410 nm, associated with 5d–4f transitions in Ce³⁺ ions, was observed.