THERMAL EXPANSIVITY VERSUS PRESSURE AT CONSTANT TEMPERATURE - A REEXAMINATION

Results from recent high pressure experiments have shown δT in the relationship   to be constant over significant compressions, one of the original assumptions required to make this relationship valid. We have re‐examined the original derivation of this equation and present a simpler derivation eliminating the previous assumptions. Furthermore, high pressure experiments find (∂lnα/∂lnρ)T is equal in value to l/αKT(∂KT/∂T)P derived from experiments at ambient pressures. From values of −δT = l/αKT(∂KT/∂T)P at high temperatures, it is asserted that −(∂lnα/∂lnρ)T must lie between 4 and 6 in the lower mantle, a value significantly higher than previously assumed in earth models. Copyright 1990 by the American Geophysical Union.