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X-Ray Absorption Near Edge Spectroscopy for warm dense matter


Détail de l'offre

Informations générales

Entité de rattachement

Situé à 40 km au sud de Paris, le centre DAM-Île de France, a en charge la conception des armes nucléaires françaises, la recherche et développement dans le domaine de la lutte contre la prolifération et le terrorisme, l'alerte aux autorités en cas de séisme, de tsunami ou d'essai nucléaire étranger, la construction et le démantèlement de grandes infrastructures nucléaires. Leader français de la simulation numérique et du calcul intensif, il possède deux des machines européennes les plus puissantes. Il dispose également de plusieurs accélérateurs et de nombreux moyens techniques et expérimentaux pour mener ses recherches. Lui est également rattaché, l'Unité Propulsion Nucléaire située sur le centre CEA/Cadarache en région Provence Alpes-Côte d'Azur, où sont implantées les installations d'essais et une partie des fabrications de la propulsion nucléaire.  

Référence

2022-21072-S0656  

Description du poste

Domaine

Physique du noyau, atome, molécule

Contrat

Post-doctorat

Intitulé de l'offre

X-Ray Absorption Near Edge Spectroscopy for warm dense matter

Sujet de stage

X-Ray Absorption Near Edge Spectroscopy for warm dense matter

Durée du contrat (en mois)

2 ans

Description de l'offre

The study of Warm Dense Matter (WDM) is a challenging field that is at the crossroads between condensed matter and plasma physics. XANES (X-ray Absorption Near Edge Structure) is a standard technique in condensed matter physics measurements which brings valuable information on electronic and ionic structure. This technique was recently extended to WDM regime. We showed (both theoretically and experimentally) that a precise description of X-ray absorption spectrum is a key diagnostic to follow the complex mechanism of phase transition. XANES absorption are computed using Density Functional Theory combined within the framework of Projected Augmented-Wave and linear response theory. This description makes use of frozen core approximation which severely limits the description for extreme pressure conditions (~100GPa and above). The challenge is now to go beyond the frozen core approximation keeping in mind that an all electrons calculation is numerically out of reach for this extreme conditions.
The position of the edge in the absorption spectrum is connected to the energy difference between the DOS and the core orbital. Both undergo variations with temperature and density that we have to take into account to describe a possible energy shift of the absorption features when modifying the thermodynamical conditions. This is mandatory to be able to compare theoretical and experimental spectra. This is challenging using PAW and frozen core approximation. One promising possibility is to make possible the relaxation of the core orbitals consistently with the valence electrons.
During this post-doc, the candidate will have to run DFT based molecular dynamics simulations on massively parallel computers to obtain the properties of metals in extreme pressure (T>10000K) and temperature (P>100GPa). Implementation will be necessary to improve the description of XANES spectra for this extreme condition. All implementation and calculation will be done with ABINIT code. All this work will be done with a close interaction with experimental teams.

Profil du candidat

The candidate must have a strong expertise in solid states physics. He or she should have an experience in ab initio molecular dynamics simulation. A good knowledge on programming is also necessary.


Thèse

Localisation du poste

Site

DAM Île-de-France

Localisation du poste

France, Ile-de-France, Essonne (91)

Ville

Bruyères-le-Châtel