Dynamical and optical properties of rare phenakite mineral: A combined experimental and computational study

The electronic structure, optical and dynamical properties of the natural phenakite Be2SiO4, are studied using ab initio calculations completed by Raman spectroscopy experiments. The calculated structural properties are in excellent agreement with experimental data and are accompanied by chemical bonds analysis using Maximally Localized Wannier Functions method. The theoretical analysis of projected density of states reveals the nature of the valence band as composed by electronic states of oxygen atoms, while conducting band is composed by electronic states of Si-atoms. Using linear response method the optical properties are calculated and compared with optical properties of quartz. It was shown the similarity of rare phenakite crystal and quartz. The calculated phonon dispersion structure reveals mostly delocalized nature of phonon states with quasilocalized phonons in high-frequency range, where the most intense band in Raman spectrum is observed. The band is ambiguously assigned to the breathing mode in SiO4 tetrahedra. Basing on such peculiarity in the spectra the rapid nondestructive diagnostic method of the sample is purposed. [Display omitted] •The Be2SiO4°° polarized Raman spectra were measured experimentally and interpreted using ab initio calculations for the first time•The quasi-localizedmodes in SiO4°tetrahedra° are revealed in high-frequency range•According to Wannier functions analysis, it was found that valence electrons are localized in vicinity of oxygen atoms positions and valence state of O atoms exhibits sp2 hybridization.•The calculated values of effective mass of holes four times higher than effective mass of electrons, therefore the charge transfer is mostly due to electrons transport.•The express method ofcomposition diagnostic based on Raman spectroscopy is developed