P‐V‐T equation of state of periclase from synchrotron radiation measurements

The volume of periclase (MgO) has been measured by monochromatic X‐ray diffraction in a laser‐heated diamond anvil cell up to a pressure of 53 GPa and a temperature of 2500 K. The X‐ray source was synchrotron radiation at the European Synchrotron Radiation Facility (Grenoble, France). In addition to laser heating, the use of argon as a pressure transmitting medium provided quasi‐hydrostatic conditions in the cell assembly. In order to take thermal pressure effect into account, pressure was measured using an internal pressure calibrant (platinum). By analysis of the experimental P‐V‐T data set the following parameters were obtained: at ambient temperature, K′ 0 = 3.94 ± 0.2 when K 0 is fixed to 161 GPa (with a Birch‐Murnaghan equation of state); under high temperature, α( P = 0, T ) = (3.0 + 0.0012 T ) × 10 −5 K −1 ; (∂ K T /∂ T ) P = −0.022(3) GPa K −1 . The quasi‐harmonic Debye model appears to describe correctly the temperature dependence of the volume at high pressure within experimental errors, with the following parameters: θ D 0 = 800 K, γ 0 = 1.45 (Grüneisen parameter under ambient conditions), and q = 0.8 ± 0.5.