Structure, elasticity and stability of reidite (ZrSiO_4) under hydrostatic pressure: A density functional study

摘要

We investigate the lattice parameters, elastic constants and the stability of ZrSiO_4 phases using plane wave implementation of the density functional theory within the framework of local density approximation (LDA). ZrSiO_4 occurs as a stable tetragonal phase (zircon, 141/amd) in the ambient condition, which undergoes a transition to reidite phase (I41/a) at a pressure of 7.3 GPa. Our study predicts that the silicate phase can experience another transformation (reconstructive phase transition) to a phase with wolframite structure (P2/c) at 75.8 GPa. Electronic band gaps of zircon and reidite widen with pressure, whereas that of wolframite declines at a threshold pressure (72 GPa). The bulk modulus of reidite steadily increases with pressure, but its shear modulus follows a quadratic variation, showing drops at pressures >75 GPa. Finally, we interpret that the reidite to wolframite transition results from increasing cation-cation repulsive forces and negative pressure derivatives of shear modulus.