Sound velocity of liquid Fe-alloys

Sound velocity and elasticity measurements at high pressure and high temperature are very challenging for solid metals, and all the more for liquid metals. Inelastic x-ray scattering (IXS) has been proven to be a suitable technique to study elasticity and sound velocity of solid samples under extreme conditions. The feasibility of applying IXS to liquid metals in combination with laser heated diamond anvil cell has been recently proven as well. Therefore, IXS will be used to measure the sound velocities of liquid Fe-alloys. IXS measurements are, however, very time consuming and hardly compatible with systematic work on many samples in the binary (Fe-S, Fe-Si, Fe-C) and ternary (Fe-S-Si and Fe-S-C) systems. Thus, IXS measurements will be complemented by picosecond acoustic measurements. The ability of picosecond acoustics to probe sound velocity of liquid metals at moderate pressure and temperature (up to ~10 GPa and ~600 K) has been recently demonstrated. The challenge will be to extend the method to significantly higher P-T implementing by application of picosecond acoustics in combination with novel generation resistively heated diamond anvil cell  (T up to ~1600 K), and in combination with laser heating (T up to ~4000 K).

Such technical advancements will allow measurements of sound velocities of liquid Fe-alloys over an extended P-T range. The results will allows me to propose direct density and velocity models for the liquid core of telluric planets as a function of the size and compositions. Furthermore the direct comparison of adiabatic compressibility (from sound velocity measurements) and isothermal compressibility (from x-ray diffraction) will allow estimation of the Grüneisen parameter for the liquid Fe-alloys, which controls an adiabatic core temperature profile.