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Dipartimento di Fisica - Politecnico di Milano

Melting curve determination under extreme conditions by laser acoustics [IMPMC, Parigi]

Melting curve determination under extreme conditions by laser acoustics

Sorbonne Université, campus Pierre et Marie Curie, IMPMC (Institut de minéralogie, de physique des matériaux et de cosmochimie)

Phase diagrams are central for both fundamental and applied physics
and chemistry, as is understanding how materials’ properties changes with pressure- and
temperature-induced structural modifications. In particular, the determination of melting
curves under extreme conditions has been attracting a lot of interest with direct implications
for both materials science and planetary science. Indeed, just as few examples, melting curves
bring information on exotic phenomena such as liquid-liquid phase transitions and place
constraints in the thermo-chemical evolution and crystallization mechanisms of planets.
The experimental determination of melting curves at pressure in the Mbar range is however
technically challenging. Few protocols have been recently established, but they all call for the
use of synchrotron techniques, which strongly limits the number of studies that can be
performed. Here we propose to overcome these limitations by use of a laboratory-based
technique combining diamond anvil cell for pressure generation, laser heating for
temperature generation, and picosecond acoustics for melting determination. As both optical
reflectivity and the sound velocity highly depend on the liquid vs. solid nature of the sample,
and even a small fraction of melt can largely influence such physical properties, ultra fast laser
acoustics stems as very powerful melting diagnostic of samples under extreme conditions.
An experimental setup, unique in the world, has been recently fully implemented at IMPMC.
This master internship aims at developing the protocol for melting determination performing
measurements on reference metals (e.g. Mo, Ti, Ni, Co) and then applying it for the studies of
iron and iron-alloys of direct interest for the core of Mercury and Mars.
This internship is carried out within the frame of the InSight NASA Discovery program mission
currently operating on Mars, and the ERC-funded project PICKLE (Planetary Interiors
Constrained by Key Laboratory Experiments).

Techniques/methods in use: diamond anvil cell, laser heating, luminescence,
spectroradiometry, picosecond acoustics

Applicant skills: Interest for experimental activity; Motivation to work on a project at the
frontiers between materials science and planetary science.

Internship supervisor(s): Daniele Antonangeli (; 01 44 27 52
22); Silvia Boccato (