Deep Earth Chronicles: High-Pressure Investigation of Phenakite Mineral Be2SiO4.

ABSTRACT

Beryllium silicate, recognized as the mineral phenakite (Be2SiO4), is a prevalent constituent in Earth's upper mantle. This study employs density-functional theory (DFT) calculations to explore the structural, mechanical, dynamical, thermodynamic, and electronic characteristics of this compound under both ambient and high-pressure conditions. Under ideal conditions, the DFT calculations align closely with experimental findings, confirming the mechanical and dynamical stability of the crystalline structure. Phenakite is characterized as an indirect band gap insulator, possessing an estimated band gap of 7.83 eV. Remarkably, oxygen states make a substantial contribution to both the upper limit of the valence band and the lower limit of the conduction band. We delved into the thermodynamic properties of the compound, including coefficients of thermal expansion, free energy, entropy, heat capacity, and the Gruneisen parameter across different temperatures. Our findings suggest that Be2SiO4 displays an isotropic behavior based on estimated anisotropic factors. Interestingly, our investigation revealed that, under pressure, the compression of phenakite is not significantly affected by bond angle bending.