P-V-T EQUATION OF STATE OF MAGNESIOWUSTITE (MG0.6FE0.4)O

The lattice parameter of magnesiowustite (Mg0.6Fe0.4)O has been measured up to a pressure of 30 GPa and a temperature of 800 K, using an external heated diamond anvil cell and diffraction using X-rays from a synchrotron source. The experiments were conducted under quasi-hydrostatic condition, using neon as a pressure transmitting medium. The experimental P-V-T data were fitted to a thermal-pressure model with the isothermal bulk modulus at room temperature K(T0) = 157 GPa, (partial derivative K(T0/partial derivative P)T = 4, (partial derivative K(T)/partial derivative T)p = -2.7(3) x 10(-2) GPa/K, (partial derivative K(T)/partial derivative T)v = -0.2(2) x 10(-2) GPa/K, and the Anderson-Gruneisen parameter delta(T) = 4.3(5) above the Debye temperature. The data were also fitted to the Mie-Gruneisen thermal equation of state. The least-squares fit yields the Debye temperature theta(D0) = 500(20) K, the Gruneisen parameter gamma-0 = 1.50(5), and the volume dependence q = 1.1 (5). Both thermal-pressure models give consistent P-V-T relations for magnesiowustite to 140 GPa and 4000 K. The P-V-T relations for magnesiowustite were also calculate by using a modified high-temperature Birch-Murnaghan equation of state with a delta(T) of 4.3. The results are consistent with those calculated by using the thermal-pressure model and the Mie-Gruneisen relation to 140 GPa and 3000 K.