Equation of state of MgSiO 3 with the perovskite structure based on experimental measurement

We studied MgSiO 3 with the perovskite structure heated to temperatures up to 1500 K at pressures between 36 and 110 GPa with in-situ X-ray diffraction. The new pressurevolume-temperature (P-V-T) data were combined with literature data to provide thermal expansivity α and compressibility β against T (in K): α T =2.71 × 1O -5 + 1.80 × 1O -9 T - 1.48 T 2 (Model 1) or α T =2.13 × 1O -5 + 7.57 × 10 -9 T- 1.02 T 2 (Model 2), and β T = 3.735 × 10 -7 + 3.27 × 1O -11 T + 6.60 × 1O -15 T 2 . Model 1 yields physical properties of perovskite that confirm Anderson’s (1998) Debye approach; the model is valid for extrapolation to 3000 K or more. The parameters at 300 K are: α = 1.1 × 1O -5 , K 0 ′ (bulk modulus) = 261 GPa, K′ 0 = 4 and (∂K/∂T) p = -0.027. Thermal expansivity from this model does not fit the data of Funamori et al. (1996) at high temperature for P = 25 GPa. Model 2 uses an equation for α based on the data of Funamori et al. (1996), fits the available experimental data closely, and maintains conformity with Anderson’s Debye ap­proach. Heat capacity, C p , data for perovskite is given by either: C p = 110.8 + 8.031 × 1O -3 T - 1.302 × 1O -7 T 2 - 1.647 × 1O 7 T 2 + 2.755 × 1O 9 T -3 + 267.5 T -0.5 + 9287 T -1 (Model 1) or C p = 121.33 + 2.77 × 10 -3 T - 2.585 × 1O -6 T 2 - 1.710 × 1O 7 T + 2.792 × 1O 9 T -3 - 169 T -0.5 + 15782 T -1 (Model 2).