Thermal expansion of liquid Fe-S alloy at high pressure

Abstract

Highlights-Density of liquid Fe-S alloys has been measured under high pressure as a function of temperature by in situ X-ray diffraction in multi-anvil press.-Thermal expansion of liquid Fe-S alloys has been determined up to 7 GPa and 2200 K.-Top-down crystallization is the most likely scenario for Fe-FeS cores of planetesimals and small planets.

Measuring the melting curve of iron at super-Earth core conditions

“…These observations reaffirm the expected phenomena of bottom-up core solidification, where dynamo simulations show that the presence of bottom-up solidification will produce stronger magnetic fields than in the alternative case of top-down solidification (17). Furthermore, our observation of hcp iron along the melt curve combined with that of Turneaure et al (8) refutes predictions of body-centered cubic stability in pure iron at core conditions (18,19), where it is noted that substantial alloying can affect phase stability and the mode of core solidification (20). Finally, the solidification into a mixed phase suggests that the nanosecond time scale of the experiments is not causing the transition to be substantially overdriven, where we might only expect to see a liquid or completely solidified system (14,15).…”

“…Furthermore, our observation of hcp iron along the melt curve combined with that of Turneaure et al . ( 8 ) refutes predictions of body-centered cubic stability in pure iron at core conditions ( 18 , 19 ), where it is noted that substantial alloying can affect phase stability and the mode of core solidification ( 20 ). Finally, the solidification into a mixed phase suggests that the nanosecond time scale of the experiments is not causing the transition to be substantially overdriven, where we might only expect to see a liquid or completely solidified system ( 14 , 15 ).…”

Amorpheus: a Python-based software for the treatment of X-ray scattering data of amorphous and liquid systems

“…Later on, the treatment has been adapted to high-pressure measurements by Sanloup et al [6] and Eggert et al [7], extending the analysis of x-ray diffraction to fluids in diamond anvil cell (DAC), and by Funamori et al [8,9] for the analysis of energy dispersive x-ray diffraction in large volume presses. More recently, the method has been fully exploited thanks to the use of a combined angular and energy dispersive x-ray diffraction (CAESAR) technique coupled to large volume presses [10][11][12]. As today, liquid diffuse scattering have been measured under static and dynamic high-pressure conditions for a large variety of amorphous and liquid systems, be these alloys, mono-atomic, molecular or polymeric systems (e.g.…”

“…As today, liquid diffuse scattering have been measured under static and dynamic high-pressure conditions for a large variety of amorphous and liquid systems, be these alloys, mono-atomic, molecular or polymeric systems (e.g. [6,11,[13][14][15][16][17][18][19][20][21]) Measurements of S(Q) and g(r) as a function of pressure and temperature allow the determination of compressibility (e.g. [22]) and thermal expansion (e.g.…”

“…[22]) and thermal expansion (e.g. [11]) of liquid systems and the detection of amorphous-amorphous or liquid-liquid phase transitions (e.g. [18,21,[23][24][25]).…”