Job offers

 

Master 2 Offers
Calculs ab-initio de propriétés mécaniques de nouveaux composés sulfures de terres rares à fort potentiel optique et mécanique

Supervisors: Dr. Bruno FONTAINE, Jean-François HALET, Régis GAUTIER, Odile MERDRIGNAC-CONANEC

E-mail: bruno [dot] fontaineatensc-rennes [dot] fr, haletatuniv-rennes1 [dot] fr, rgautieratensc-rennes [dot] fr and odile [dot] merdrignac-conanecatuniv-rennes1 [dot] fr

Full proposal: 

Proposal_FONTAINE - (83.4 KB)

Le projet de stage se situe dans le domaine de la chimie théorique appliquée à
la chimie du solide. Il vise à utiliser les possibilités offertes par la
simulation numérique au moyen de méthodes de chimie quantique pour prédire les
performances mécaniques de nouveaux matériaux céramiques présentant des
propriétés optiques et mécaniques leur permettant d’être développés pour des
environnements sévères. Seront plus particulièrement étudiés, des sulfures
de terres rares qui adoptent un arrangement structural cubique (isotropie
optique) du type Th3P4. Il s’agira plus précisément d’élaborer, à l’aide des
codes de calcul de chimie quantique VASP et Wien2k, un protocole
permettant de déterminer certaines propriétés mécaniques (module de Young,
constantes élastiques, ...).

Structure et processus de céramisation de verres de chalcogénures par dynamique moléculaire

Supervisors: Dr. Eric FURET

E-mail: eric [dot] furetatensc-rennes [dot] fr

Full proposal: 

Proposal_FURET - (1 MB)

Les verres sont des matériaux connus de longue date qui continuent de susciter
des innovations constantes à l’heure actuelle. On les retrouve aussi bien dans
le secteur de la construction, dans l’automobile, dans les télécommunications
avec les fibres optiques ou encore, en tant que matrice pour le stockage de
déchets ultimes. Il s’agit alors le plus souvent de verres d’oxydes, dérivés
plus ou moins complexes de verres de silice. Plus récemment, de nouvelles
familles de verres dits spéciaux ont été développées au sein de l’équipe Verres
et Céramiques de l’Institut des Sciences Chimiques de Rennes. Elles reposent sur
la combinaison de soufre/sélénium/tellure et d’éléments adjacents du tableau
périodique pour donner des matériaux dotés de propriétés photo-induites
originales (transition réversible amorphe-cristal sous irradiation laser,
photofluidité, photodilatation ...). Ces propriétés leur autorisent de nouveaux
champs d’application comme le codage optique d'information (DVD), la réalisation
de mémoires non-volatiles, comme c'est le cas dans le système Ge-Sb-Te 
, ou le stockage de l’énergie en tant qu’électrolytes de batteries. En
dépit de leurs multiples qualités, la caractérisation structurale des verres
constitue cependant toujours un challenge de nos jours car, les méthodes de
diffraction ne sont pas aussi pertinentes qu’avec les cristaux. Il est alors
difficile d’interpréter précisément l’origine des propriétés observées, puis de
les optimiser de façon rationnelle. L’objectif du stage est de combler cette
lacune et d’étudier, au moyen de simulations par dynamique moléculaire, les
processus de vitrification/céramisation de verres de chalcogénures. Nous
intéresserons plus particulièrement à une nouvelle famille de verres dans le
système Ga-Sb-Se.

Etude théorique de nanoclusters de cuivre et d’argent hétéroleptique

Supervisors: Dr. Samia KAHLAL and Dr. Jean-Yves SAILLARD

E-mail: samia [dot] kahlalatuniv-rennes1 [dot] fr and saillardatuniv-rennes [dot] fr

Full proposal: 

Proposal_KAHLAL - (255.16 KB)

Depuis une bonne dizaine d’années les nanoclusters des métaux du groupe 11 (d10
s1) font l’objet d’un très grand intérêt (et qui va toujours croissant) de la
part de la communauté des chimistes inorganiciens. Cela est dû à leur nature
originale et à leurs propriétés spécifiques qui les placent entre les espèces
moléculaires simples et les solides divisés. Ils sont généralement constitués
d’un cœur [Mn]x+ (x < n) protégé par des ligands inorganiques (thiolates,
halogénures, hydrures,alkynyle, phosphines...). La liaison à l’intérieur du cœur
métallique est assurée par les n-x électrons provenant des orbitales de valence
s. Leur nombre obéit à des règles de décompte électronique provenant du modèle
du superatome. En effet, la structure électronique d’un nanocluster de forme
sphérique est dans une certaine mesure comparable à celle d’un atome. Il est
aussi possible d’assembler des superatomes pour faire des supermolécules
comparables à de simples molécules. Le sujet de ce stage porte sur l’étude
théorique (calculs en méthode DFT) de nouveaux superatomes et supermolécules de
cuivre et d’argent protégés par des ligands de nature différente (clusters
hétéroleptiques), notamment, dicalcogénolates, alkynyles, hydrures et
phosphines. Ce travail se situe dans le cadre d’une collaboration étroite avec
une équipe de chimistes expérimentaux (Prof. Chen-Wei Liu, NDHU, Taiwan). Il
s’agit, en combinant des ligands de charge différente, de stabiliser des cœurs
[Mn]x+ différents, et donc des nucléarités différents avec des architectures
inconnues à ce jour. Le stagiaire aura pour but de rationaliser ces structures
nouvelles et certaines propriétés associées. Le sujet bibliographique portera
sur la théorie sous-tendant les concepts de superatomes et supermolécules et sur
le rôle joué par les ligands dans leur stabilisation.

PhD Offers
Theoretical modelling of solid-state batteries

Supervisors: Eric FURET and Xavier ROCQUEFELTE

E-mail: eric [dot] furetatensc-rennes [dot] fr and xavier [dot] rocquefelteatuniv-rennes [dot] fr

Full proposal:

2023-PhD-LiBatt-CTI.pdf - (318.04 KB)

Nowadays, electricity storage is of paramount importance, notably in the context of Greenhouse effect and carbon footprint reduction. From this point of view, the increase of battery efficiency and power has attracted a great deal of attention. The challenges to be met are numerous and require a better understanding of the materials involved (electrodes and electrolytes) as well as the device interfaces.

The main objective of this thesis is to theoretically investigate all-solid-state batteries based on Lithium or Sodium. This technology has become reality since the discovery of electrolytes exhibiting high ionic conductivities that were comparable to liquid ones. Such approach offers various advantages due to their better electrochemical stability and energy density (exceeding Li-Ion batteries by more than 50%). However, instabilities at the interfaces or dendrites formation at the anode lead to degradation of the performance and/or lifetime of this type of all-solid-state batteries.

The main stages of the thesis will consist in quantum modelling based on density functional theory (DFT). More precisely, the positive electrode will be investigated by means of periodic codes such as VASP, CASTEP and WIEN2k. The atomic scale structure of glassy electrolytes will be characterized using ab initio molecular dynamics within the Car-Parrinello formalism. Fig 1. contains the glassy structure of a typical LIPON-type electrolyte at room temperature and exhibits the POxNy (x+y=4) interconnected tetrahedras. The understanding of the interfaces evolutions processes will be also considered in a second step. All the theoretical results willl be confronted to experimental data (NMR and vibrational spectra specifically) acquired during experimental investigations performed by the Glass & Ceramics team of the Rennes Institute of Chemical Sciences (ISCR).

LiPON cell

Fig. 1: (a) Structure of a 333 atoms LiPON cell@1300K; Li (pink); P (orange); O(red), N(blue) and (b) selected radial distribution functions (black line) together with their respective integration (red line). (c) Comparison of an experimental Raman spectrum (black curve) of Ga2Se3 with the DFT frequencies (red lines) calculated using GGA functional.

 

 

Ab initio Modelling of excited-state absorption

Supervisors: Boris LE GUENNIC (ISCR) and Denis JACQUEMIN (CEISAM)

E-mail: boris [dot] leguennicatuniv-rennes [dot] fr and denis [dot] jacqueminatuniv-nantes [dot] fr

Full proposal: 

phd_position_LeGuennic_Jacquemin.pdf - (246.3 KB)

The PhD project focuses on the accurate modelling of Excited-State Absorption (ESA) in - conjugated organic molecules. ESA, as its name implies, takes place when a photon is absorbed from a low-lying electronic excited state inducing the promotion of the molecular system to a higher-lying one. ESA therefore goes beyond classical linear optics (absorption and fluorescence) and is key to several experimental phenomena, including i) transient spectroscopy in which the position, intensity, and shape of ESA bands are commonly used to identify the nature and relative energies of electronic states, and hence to grasp key photophysical events occurring in photoactive materials used in solar cells, OLEDs...; ii) optical power limiting devices in which ESA is typically combined to multi-photon absorption to obtain an absorption cross-section that is supralinearly increasing with respect to the intensity of the incoming light. On the theoretical side, while the oscillator strengths (transition probabilities) corresponding to ESA can be obtained with various approaches including Quadratic-Response Time-Dependent Density Functional Theory (QR-TD-DFT), ESA has been much less explored than linear phenomena, and its simulation comes with specific challenges. To fill this gap, the PhD project has three main objectives: i) to provide reliable benchmark values for ESA transition probabilities, using very high-level of theories and to define a computationally- tractable protocol (TD-DFT) providing accurate ESA transition energies and oscillator strengths; ii) to develop a solvation model suited for quantifying the environmental effects on ESA; iii) to design improved dyes, e.g., systems in which the S1-S2 gap is exactly half of the S0- S1 gap, and showing a very strong ESA oscillator strength for the former transition, as such compounds would be ideal for optical power limiting devices. At the end of the PhD, the results obtained should allow: i) to provide to the theoretical community a series of tools allowing to model excited-state absorption with the same ease as standard one-photon absorption for any organic dye; ii) to model ESA in experimentally-relevant compounds, and to provide synthetic chemists with some design rules for ESA.

The PhD student will be working in stimulating scientific environments in both the theoretical chemistry teams in Nantes and Rennes, with team seminars and frequent scientific discussions. She/He will be co-supervised by Denis Jacquemin (CEISAM) and Boris Le Guennic (ISCR) and will be part of the LUMOMAT Academy and member of an active student network.

Applicants

The applicant should have a master in physics/chemistry or in computational/theoretical chemistry. Proven experience in quantum chemistry and knowledge in scientific computing or programming (Python) would be highly appreciated. The candidate should have a strong interest in light-matter interactions, in spectroscopies, and in methodologies. Excellent oral and written communication skills are necessary. Applications should be addressed to boris [dot] leguennicatuniv-rennes1 [dot] fr and Denis [dot] Jacqueminatuniv-nantes [dot] fr with a CV, a cover letter describing their research interests and motivation, and the names of two reference persons.

 

 

Electronic structure of novel photo-active materials for sustainable energy applications

Supervisors: George VOLONAKIS

E-mail: yorgos [dot] volonakisatuniv-rennes [dot] fr

Full proposal: 

2023-PhD_Volonakis.pdf - (225.95 KB)

A full-time PhD position is available at the Institute of Chemical Sciences of Rennes (ISCR) of the Université de Rennes (UR). The successful candidate will be supervised by George Volonakis of the CTI group. The position is for three years starting as early as October 2023, with a funding from the PIs projects, and will be supported by the established research team at Rennes working on the computational methods for energy applications.

Scientific background

Within todays critical need for sustainable and environmental-friendly energy, this project aims to employ a computational design approach to identify and accurately model the most promising novel materials for energy applications. In particular, within this thesis the candidate will work towards a deep fundamental understanding of the most critical structural, optical and electronic properties of selected materials that pioneer the next generation opto-electronic energy devices. The candidate

will employ advanced computational approaches based on first-principles to unveil the structure-property relations of prototype energy related prototype materials like halide perovskites and closely related perovskitoids and explore the materials phase-space well beyond these crystal lattices. The project supports the active research-axis of the principal investigator (PI) that has been established and developed over the past three years at the ISCR, and lead to several publications, as well as the design of novel materials like halide double perovskites, vacancy ordered double perovskites and Ag/Bi double salts. This PhD aims to identify and synthesize novel semiconducting materials and reveal known overlooked compounds with tailored properties that could advance a range of energy applications like solar-cells, photo-catalysts and light-emitters.

Profile of the candidate

A degree in Physics, Chemistry, Materials Science or closely related field is required. A strong background in any of the following subject is desired: solid-state physics, quantum-chemistry, materials modelling approaches, and atomistic simulations. The successful candidate should be highly motivated, with excellent communication skills and the ability to work in close collaboration with other theoreticians and experimentalists.

How to apply

Applications are open and candidates are encouraged to email at the soonest George Volonakis: yorgos [dot] volonakisatuniv-rennes [dot] fr, with a CV, including clear description of previous research experience, and a motivation letter.

Important dates

March 2023: Position open.
April 2023: Notification of the candidates and interviews.
October 2023: start of the thesis.

Postdoc Offers
Currently there are no open postdoc positions.