Une offre de stage de Master 2 au Département Théorie et Simulation Numérique

Sujet : Calculs quantiques des propriétés optiques d’agrégats de métaux nobles

Title : « Quantum Calculations of Optical Properties of Noble-Metal Clusters »

Description :

Simulation / modelling consists in the use of basic theory – quantum mechanics, in this case – in order to describe and understand realistic objects by means of numerical algorithms and computer codes derived from the theory.

Owing to their exceptional properties, metallic clusters and nanoparticles are used in a wide range of applications: ranging from nanophotonics, photovoltaics, catalysis, to biomarkers, uses in cancer therapy, and many others. Many NPs can be used as “antennas” because they exhibit a collective oscillation of the electrons called the surface-plasmon resonance (SPR) [1]. The use of the SPR for a particular application necessitates a good understanding of its dependence on size, shape, composition, and environment [2-4]. In addition, many of these objects are stabilized by ligands which make them very stable but also complex systems.

The goal of the present project is to study the electronic and optical properties of noble-metal clusters smaller than 2nm using time-dependent density-functional theory (TDDFT) [5].

In the modelling of ligand-protected clusters, the ligands are often simplified and reduced. These simplifications lead to changes in the results which need to be well understood and controlled. The project will study metal clusters and analyze the effect of composition and ligand termination on the electronic and optical properties. In particular, the nature of the super-atom states (angular-momentum components) will be studied, beautifully illustrating some elements of text-book-like physics in realistic systems! Calculations will be carried out using the computer codes VASP (relaxation) and octopus (TDDFT) and in addition the writing of post-processing tools to analyze the output from the above-mentioned codes.

The project will be carried out in the context of a collective reasearch at national and international lever, owing to the collaborations of H.-Ch. Weissker with other groups carrying out theoretical and experimental research. It might be followed by a PhD thesis.

Expected profile: the student is expected to have a background in solid-state and/or theoretical physics and an interest in the computer-based treatment of physical problems.

 Laboratory: CINaM / AMU (Campus de Luminy)

 Scientific Responsible:      Hans-Christian Weissker

e-mail: weissker@cinam.univ-mrs.fr

Tel: 06-62 90 38 50

[1] H.A. Atwater and A. Polman, Plasmonics for improved photovoltaic devices, Nat Mater 9, 865 (2010).

[2] A. Campos, N. Troc, E. Cottancin, M. Pellarin, H.-Ch. Weissker, J. Lermé, M. Kociak and M. Hillenkamp, Plasmonic quantum size effects in silver nanoparticles are dominated by interfaces and local environments. Nature Physics 15, 275–280 (2018).

[3] H.-Ch. Weissker, H. Barron Escobar, V.D. Thanthirige, K. Kwark, D. Lee, et al. Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster. Nature Communications, 2014, 5, p. 3785.

[4] X. López-Lozano, C. Mottet et H.-Ch. Weissker, Effect of Alloying on the Optical Properties of Ag-Au Nanoparticles,  J. Phys. Chem. C 117, 3062 (2013).

[5] Time-Dependent Density-Functional Theory: Concepts and Applications, C. Ullrich, Oxford University Press (2012).