Description du sujet de thèse

Context: Liquid argon (LAr) detector technology has undergone impressive development in recent years in astroparticle and medical physics. Its high scintillation and ionization yields, radiopurity, and scalability make it an ideal target in the search for interactions with energies
ranging from tens of eV to several GeV. Recent developments show that Xe-Ar mixtures can extend and improve the capacity of the LAr-based detectors. Xe-Ar detectors operate at atmospheric pressure and at temperatures for which the mixture Xe-Ar is in the liquid phase. The detector temperature is slightly lower than the Ar boiling one (87.3 K) and much lower than the Xe triple point temperature (161.4 K). As a consequence, the maximum Xe content in the Xe-Ar mixture is imposed by the solubility limit of solid Xe in LAr. To determine this limit and the temperature-pressure region of existence of the Xe-Ar liquid phase, the precise knowledge of the Xe-Ar phase diagram is required. Although noble gases have been widely studied, only few literature data exist for Xe-Ar mixture. The PhD project aims to investigate the thermodynamic properties of this mixture by using classical molecular simulations. It is part of a bigger project called X-ART granted by the French agency of research (ANR) dedicated to the development of Xe-Ar detectors.
Objectives: Thermodynamic and transport properties of the Xe-Ar mixture will be studied by molecular simulation techniques (Monte-Carlo simulations and molecular dynamics), giving molecular insight of the system and its behavior when submitted to changes in external conditions. In particular, the liquid-solid transition of the Xe-Ar mixture, the mechanism of nucleation and crystallization of the Xe-rich solid phase, and the local organization of molecules in the liquid phase will be studied. A part of this study will be inspired by the recent development around the Kirkwood-Buff Integrals which makes the link between local structure and thermodynamics [J. Chem. Phys. 157, 130901 (2022)]. The results will be used in collaboration with experimentalists to develop an accurate equation of state of Xe-Ar mixtures in the whole phase diagram.
Expected skills of the candidate: Master degree in physics, physical chemistry, chemical processes or related field. Good knowledge of thermodynamics. Basics in statistical mechanics. Experience in programming and / or numerical simulations is an advantage.
Supervisors:
1) Dr. Jean-Marc Simon, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Dijon France
2) Dr. Céline Houriez, Centre de Thermodynamique des Procédés, ecole des mines de Paris

Contexte de travail

The PhD student will work in the INTERFACES department composed of 23 permanent staff, including 19 professors and researchers, as well as 4 engineers and technicians, and more particularly with the Adsorption on Porous Solids team led by I. Berzverkhyy. This team is composed of 7 researchers/teaching researchers who study the adsorption of volatile molecules on porous materials (MOF, zeolite, ...) by experimental approaches and molecular modeling. It is this modeling aspect that will be emphasized in the thesis which will be done partially (1/3 of the time) in Fontainebleau at the Centre de Thermodynamique des Procédés, of the Ecole des Mines de Paris. This center is specialized in thermodynamic measurements and determination of equation of state based also on molecular modeling.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.