Melting and thermal expansion of iron in uniformly laser-heated diamond anvil cells

Abstract

A technique is described to laser heat samples uniformly under hydrostatic pressure conditions to over 2500 K and 400 kbar with very high accuracy in P and T. I re-measured the melting curve of iron by this technique and obtained excellent agreement with my earlier work using resistive wire heating (Boehler 1986). P-V-T measurements on γ-iron to 200 kbar and 2000 K using synchrotron radiation leads to a strong decrease of the thermal expansion coefficient with pressure, (∂lnα/∂lnV)_T = 6.5. The zero pressure bulk modulus K₀ decreases with temperature by 0.33 kbar deg⁻¹. This Yields densities of iron at conditions in the Earth's core which are consistent with shock compression measurements. The potiential of studying mineralogical phase transitions by this method is described.

Key Words:

• laser heating
• iron
• melting
• equation of state
• thermal expansion