First-principles investigations of structural, elastic and electronic properties of hydrous fayalite

The structure, elasticity and conductivity of hydrous fayalite (Fe 2 SiO 4 H x ( x = 0.25, 0.5, 0.75)) are discussed based on the First-principles. Fe 2 SiO 4 H x ( x = 0.25, 0.5, 0.75) models are established by hydrogen atoms occupying the interstice space of the fayalite (Fe 2 SiO 4 ) unit cell. The optimized results show that hydrogen atoms form hydroxyl (OH − ) with the surrounding oxygen atoms in the modeling course, which is consistent with the experimental conclusion that water exists in fayalite in the form of OH − . The calculated results of the elastic constants for Fe 2 SiO 4 H x ( x = 0.25, 0.5, 0.75) show that the elastic constants increase as the pressure increases and decrease as the water content increases at 0 ∼ 30 GPa. Compared to Fe 2 SiO 4 , the ranges of compression wave velocity ( V p ) of Fe 2 SiO 4 H x ( x = 0.25, 0.5, 0.75) are 1.02 ∼ 3.52