Missions

Development of computer codes for the simulation of XRD data. XRD experiments at ESRF.

Activités

The project focuses on the analysis of the nanostructure of oxide polycrystalline materials, in particular using the upgraded Laue microdiffraction (µLaue) station of the European Synchrotron Radiation Facility (ESRF) IF beamline. µLaue is a powerful method to quantify strain at the local scale (~ 300 nm) and, with the recent development of deep learning-based indexing algorithms [1], it is able to operate in real time during in situ measurements even at high temperature [2]. One of the goal of this project is to push this technique further and analyze the intensity distribution in the vicinity of the x-ray diffraction (XRD) peaks so as to be able to quantify local strain, compositional gradients and defect densities. Computing XRD data is a two-step process. The first step involves the generation of realistic microstructures in the form of numerical cells. The second step is to compute the scattered intensity from the cells, considering the geometry of the experiment. Based on our previous work [3], this methodology will be applied to µLaue data, using numerical cells with simple model defect structures. Your work will therefore imply:
• generating numerical crystals with defects (point defects, dislocations, twin boundaries,...)
• computing the diffracted intensity in the µLaue geometry
Depending on the progress of the project, convolutional neural networks will be prototyped and trained with the data generated and tested with real data recorded at ESRF.
[1] R. R. P. Purushottam Raj Purohit, S. Tardif, O. Castelnau, J. Eymery, R. Guinebretiere, O. Robach, T. Ors, J.S. Micha “LaueNN: Neural network based hkl recognition of Laue spots and its application to polycrystalline materials” J. Appl. Cryst. 55 (2022) 737-750.
[2] R.R.P. Purushottam Raj Purohit, D. Fowan, S. Arnaud, N. Blanc, J.S. Micha, R. Guinebretière, O. Castelnau, “Laue microdiffraction on polycrystalline samples above 1500 K thanks to the QMAX furnace” J. Appl. Cryst. 57 (2024) 470-480.
[3] A. Boulle, A. Chartier, A. Debelle, X. Jin, J. -P. Crocombette, “Computational diffraction reveals long-range strains, distortions and disorder in molecular dynamics simulations of irradiated single crystals”, J. Appl. Cryst. 55 (2022) 296-309.

Compétences

We are looking for a motivated applicant holding a PhD since less than two years in condensed matter physics, material science, crystallography or other closely related fields. The successful candidate should be familiar with XRD and should have a solid experience with Python programming.

She/he will have a good communication skills and team spirit. The ability to work well in a collaborative international environment is essential.

Contexte de travail

The post doc fellow will be hired by IRCER (Unité Mixte de Recherche CNRS, UMR 7315) in Limoges, and will work in close collaboration with the PIMM lab. in Paris and the scientific staff of the IF beamline in Grenoble where the experimental work will be performed. Depending on administrative delays the position is aimed to start between the 1st July and the 1st September 2025 and is offered on a fixed-term 18 months contract.

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.