Missions

The post-doctoral researcher will participate to the ANR PYRISOFE project associating the GET (Toulouse) and IMPMC (Paris) laboratories.
The elemental and isotopic composition of sedimentary pyrites is commonly used to trace the evolution of ocean chemistry and redox state through geological times. However, the mechanisms and kinetics of pyrite formation remain poorly known. The PYRISOFE project, gathering experimental work with analytical and theoretical approaches, aims at quantifying and rationalizing the influence of trace elements on each of the crystal-chemical steps of pyrite formation in low-temperature conditions, and in particular on Fe isotope fractionation of pyrite.
From a theoretical point of view, we will study the molecular-scale interaction of trace elements such as Ni and As with the solid and colloidal iron sulfide phases involved in pyrite formation. This will require the application of atomistic simulation methods to complex natural systems. Solids will include the final product, FeS2 pyrite, but also FeS mackinawite, which occurs as a disordered solid phase. As for dissolved phases, we will focus on FexSx species and Fe polysulfide complexes, whose actual structures are still debated. Structural, electronic and energetic properties will be investigated in order to identify likely mechanisms of trace element incorporation. From there, the final objective will be to determine thermodynamic properties such as the partition coefficient of trace elements between solid and solution, and the equilibrium fractionation of iron isotopes.

Activités

The post-doctoral fellow will contribute in particular to the following aspects:
- Setting up the appropriate molecular dynamics simulations and static calculations to describe as realistically as possible the structure of the solid and colloidal phases mentioned above (codes like Quantum Espresso, CP2K, …).
- Determination of trace element partition coefficients and iron isotope fractionations.
- Collaboration and exchanges with the other members of the ANR PYRISOFE project to ensure synergy with experimental and analytical tasks.

Compétences

Candidates must hold a doctoral degree. Good experience in atomistic modeling, in particular in ab initio molecular dynamics, is essential. General knowledge of inorganic chemistry, geochemistry and mineralogy is highly desirable, as well as good communication skills and the ability to work in a collaborative project.

Contexte de travail

Géosciences Environnement Toulouse (GET, https://www.get.omp.eu) is a multidisciplinary research laboratory dedicated to improving knowledge of (i) the Earth evolution and dynamics, (ii) past and present environments and climates, and (iii) the critical zone and contaminants-environment-health interactions. The lab currently brings together around 250 people including ~160 permanent staff from the CNRS, University Toulouse III, IRD and CNES. The post-doctoral fellow will join the “Stable isotopes geochemistry” group and will work mainly in collaboration with Marc Blanchard. The post-doctoral fellow will also have strong interaction with the members of the “Environmental mineralogy” group of the IMPMC laboratory (Paris, http://impmc.sorbonne-universite.fr/fr/equipes/mineralogie_environnementale.html), in particular with Julie Aufort. The post-doctoral fellow will have access to local, regional and national computing facilities.

Contraintes et risques

/