HIGH-P,T PHYSICAL PROPERTY STUDIES OF EARTHS INTERIOR - THERMOELECTRIC-POWER OF SOLID AND LIQUID FE UP TO 6.4 GPA

High p,T experiments provide indirect access to the deep interior of Earth. High p,T research at the University of Western Ontario using large volume cubic anvil presses has focused on in-situ measurements of physical properties of mantle and core related substances as they relate to Earth's interior physical processes. Thermoelectric power measurements of solid and liquid Fe, using twisted Fe/Pt-10%Rh junctions, have been made atp up to 6.4 GPa. By isolating the sign determining energy derivative of the density of states at the Fermi energy, partial derivative N(epsilon(F))/partial derivative epsilon, in the expression for the Seebeck coefficient of Fe, these measurements show that partial derivative N(epsilon(F))/partial derivative epsilon is positive for liquid Fe atp below approximately 4.0 GPa but partial derivative N(epsilon(F))/partial derivative epsilon is negative for p above 4.0 GPa. The solid phase polymorphism which Fe exhibits in this p region, and its influence on the liquid state, is suggested as the explanation for the shea range bcc-like and fee-like properties of the liquid. This finding corroborates our earlier measurements on the p-dependence of the T-coefficient of electrical resistivity of liquid Fe, which showed a similar discontinuity at the delta(bcc)-gamma(fcc)-liquid triple point pressure.