Equation of state and structural variations of synthetic forsterite-fayalite solid solution by single-crystal X-ray diffraction

Olivine, a predominant mineral in the Earth’s upper mantle, plays a crucial role in geophysical and geochemical processes due to its abundance and elastic characteristics. This study investigates the elastic properties and structural variations of synthetic forsterite-fayalite solid solutions under high-pressure conditions through synchrotron single-crystal X-ray diffraction. A series of samples with varying fayalite contents were synthesized and characterized to evaluate the impact of Fe incorporation on unit-cell parameters, bulk modulus, and compression behavior. The results demonstrate that increasing fayalite content elongates the b-axis, increases polyhedral distortions, and enhances the bulk modulus, while maintaining the structural rigidity of [SiO₄] tetrahedra. By refining the fit parameters of the Birch-Murnaghan equation of state, this study establishes a composition-property relationship for elastic behavior. These results provide key constraints for modeling mantle dynamics and planetary evolution.