A SIMPLIFIED MODEL FOR PREDICTING HIGH-PRESSURE THERMAL-EXPANSION OF MGO

Thermal expansion of MgO, periclase, is approximated by contributions from a quasi-harmonic perfect crystal and its equilibrium high tempera ture/pressure defects. We demonstrate that the influence of thermal de fects on high pressure thermal expansion is very small and may be negl ected at lower mantle conditions. Following that, a simple relationshi p has been obtained between high pressure thermal expansion and the th ermal expansion of a quasi-harmonic perfect crystal at zero pressure. Our estimation of MgO thermal expansion at the core-mantle boundary is 9.36x10(-6)K(-1).