Elasticity of Mg2SiO4 ringwoodite at mantle conditions

The themoelastic properties of Mg2SiO4 ringwoodite at mantle pressure and temperature conditions are reported based on ab initio molecular dynamic simulations. A third-order Birch–Murnaghan equation at a reference temperature of 2000 K is defined by K0 = 138 GPa, K′0=5.2K′0=5.2, and V0(2000 K) = 560.3 Å3. The Grűneisen parameter is determined to be γ(V) = γ0(V/V0(298 K))q with γ0 = 1.22 and q = 1.44(5), with V0(298 K) = 524.56 Å3. The thermal expansion is determined to be (α/α0)=(V/V0(298 K))δT(α/α0)=(V/V0(298 K))δT in which α0 = 2.74 × 10−5 K−1 and δT = 5.2(1). The bulk modulus is temperature independent at constant volume, while the shear moduli vary with temperature at constant volume. Elastic anisotropy decreases with both pressure and temperature becoming isotropic by the bottom of the upper mantle.