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PhD: Variational QED for molecular properties

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Français - Anglais

Date Limite Candidature : lundi 22 août 2022

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General information

Reference : UMR5626-TROSAU-005
Workplace : TOULOUSE
Date of publication : Monday, August 1, 2022
Scientific Responsible name : Trond SAUE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2022
Proportion of work : Full time
Remuneration : 2135 euros gross/month

Description of the thesis topic

** Variational QED for molecular propertiess **

The PhD is part of the project HAMP-vQED [Highly Accurate Molecular Properties using variational Quantum Electrodynamics] funded by an ERC Advanced Grant.

Background : The building blocks of chemistry are organized in the periodic table, which requires quantum mechanics for its understanding. In the 1980s it was realized that in order to correctly describe the heavy elements in the lower part of the periodic table, the special theory of relativity had to be invoked. Does chemistry need more physics ? The HAMP-vQED project will investigate the possible role of quantum electrodynamics (QED) in chemistry. It will provide a protocol for highly accurate calculations of molecular properties, with particular attention to properties that probe the electron density in the close vicinity of atomic nuclei, where the QED-effects are created. The HAMP-vQED project adheres to the general framework of quantum chemistry by seeking a variational (non-perturbative) approach using local (Gaussian) basis functions.

Content : The sophisticated machinery of QED, built on perturbation theory and the iconic Feynman diagrams, can only be applied to few-electron systems. For general heavy atoms or molecules some progress has been made using effective QED potentials [1-4]. However, these effective QED potentials have been mainly constructed to provide energy corrections, and it is a very open question whether their domain of validity extends to the calculation of molecular core properties. Full-fledged QED-calculations will allow us to test this and also provide
a more satisfactory formulation of relativistic quantum chemistry. The main challenge of the project will be to cure the formalism of the singularities that always plagued QED, by appropriate renormalization techniques in coordinate space.

1. E.A. Uehling, “Polarization Effects in the Positron Theory”, Phys. Rev. 48, 55–63 (1935)
2. P. Pyykkö and U. B. Zhao, “Search for effective local model potentials for simulation of quantum electrodynamic effects in relativistic calculations”, J. Phys. B: At. Mol. Opt. Phys. 36, 1469 (2003)
3. V.V. Flambaum and J. S. M. Ginges, “Radiative potential and calculations of QED radiative corrections to energy levels and electromagnetic amplitudes in many-electron atoms”, Phys. Rev. A 72, 052115 (2005).
4. V.M. Shabaev, I. I. Tupitsyn, and V. A. Yerokhin, “Model operator approach to the Lamb shift calculations in relativistic many-electron atoms”, Phys. Rev. A 88, 012513 (2013)

La thèse requiert un candidat, formé en physique ou chimie théorique, avec une solide formation en mathématiques et prêt à s'investir dans la modélisation et la programmation.

Candidates should provide the following documents :
1) CV
2) Lettre of motivation
3) Reference letter (with ranking!). As for the ranking, we would like your reference to make a judgement on how you place in relation to the other students having done the same Master programme. E.g. are you in the top 10% or top 25 % etc. This is just indicative, and the admissions committee will focus mostly on the text of your motivation letter and CV rather than the % ranking.

Work Context

The Laboratory of Quantum Chemistry and Physics (LCPQ), Mixed Unit UMR5626 associated with the University of Toulouse III and the CNRS (Institute of Chemistry as main attachment, Institute of Physics as secondary attachment), exists under this name since January 2007.

The LCPQ currently covers several fields of Theoretical Chemistry (mainly quantum) and Theoretical Molecular Physics. An important part of its activities is located at the interface between theoretical chemistry and molecular physics. It has a strong methodological component, producing computational and simulation codes, as well as teams involved in applications to systems of physicochemical and biological interest: molecular magnetism, very high resolution spectroscopy, reactivity and photochemistry of coordination complexes and biomolecules, aggregates and nanoparticles.

The laboratory is organized into four teams:

- Methods and tools for quantum chemistry (THEO)
- Theoretical and computational photochemistry (PhotoTeC)
- Extended Systems and Magnetism (SEM)
- Modeling, Aggregates, Dynamics (MAD)

The successful candidate will be integrated in the THEO team.

Constraints and risks

Nothing to report

Additional Information

HAMP-vQED [Highly Accurate Molecular Properties using variational Quantum Electrodynamics]

Does chemistry need more physics? It has long been known that the construction of the periodic table of elements is explained by quantum mechanics, and that relativity theory must be added to properly describe the chemistry of heavy elements. The HAMP-vQED project aims at probing the role of quantum electrodynamics (QED) in chemistry by providing an approach that allows for the accurate calculation of molecular properties, with a particular focus on those that probe the electron density close to the atomic nuclei where QED effects are created. The proposed approach fits into the usual framework of quantum chemistry, namely a variational approach using local basis functions.

For more information: https://dirac.ups-tlse.fr/hamp-vqed/doku.php

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