Structural and dynamic properties of borate liquids and glasses in connection with elastic phase transition

 

Laboratories: Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), Paris, France and Institut Laue Langevin (ILL), Grenoble, France.                                                             

Address: University P. & M. Curie (UPMC), 4, Place Jussieu, 75005 Paris, France and ILL, 71 avenue des Martyrs, 38042 Grenoble, France

PhD supervisors : Dr G. Ferlat (IMPMC, Paris), Dr M. Gonzalez (ILL, Grenoble)

 

Scientific project:

Borates (such as (M2O)x-(B2O3)1-x where M is an alkali metal) enter in the composition of many technologically-important materials: electrolytes, waste glasses, bioactive materials, etc. From a microscopic point of view, the originality of borates, as compared to other glasses such as silicates, lies in the fact that boron can adopt several coordination states ([3]B or [4]B at ambient pressure) depending on the temperature and/or alkali concentration: this gives rise to original topological networks, which are made by both 2D (figure (a)) and 3D (figure (b)) superstructural units. These structural aspects are essentials to understand the many anomalies (density maxima, Tg minima) and several spectacular variations (figure (c)) of the properties with the alkali concentration x.

This project is motivated by the recent discovery (figure (c)) in (Na2O)x-(B2O3)1-x glasses, of a so-called intermediate phase, in a given concentration range (20 £ x £ 40 %) [3]. This phase is, mechanically speaking, intermediate between the rigid and flexible phases. It is characterised by many remarkable properties such as a low enthalpy of vitrification (quasi-reversible glass transition), and a reduced aging.

 

 

 

The main aim of this project is to carry out molecular dynamics simulations of borate liquids and glasses for concentrations corresponding to the 3 phases (rigid, intermediate, flexible). These simulations will be used to complement and to guide the interpretation of experiments (neutron and x-ray diffraction).

The numerical part of this work will be supervised by G. Ferlat (IMPMC, UPMC) in close collaboration with Matthieu Micoulaut (LPTMC, UPMC) and Mathieu Salanne (PHENIX, UPMC). The experimental part will be supervised by M. Gonzalez (ILL, Grenoble) in close collaboration with L. Cormier (IMPMC, UPMC) and G. Lelong (IMPMC, UPMC).

[1] G. Ferlat et al., Phys. Rev. Lett. 101, 065504 (2008)

[2] G. Ferlat et al., Nature Materials, 11, 925 (2012)

[3] K. Vignabooran et al., Europhys. Lett., 108, 56001 (2014)

[4] A. Zeidler et al., Phys. Rev. B 90, 024206 (2014)

[5] O. Alderman et al. J. Phys.: Condens. Matter, 27, 455104 (2015)

 

Location: IMPMC, Campus Jussieu in Paris and ILL, Polygone Scientifique in Grenoble (with respective proportions to define with the candidate)

Applicant skills: Solid background in solid-state physics (or statistical mechanics). A basic knowledge of molecular modelling techniques and/or quantum-chemistry calculations is a plus. Skills in programming are appreciated.

Techniques: molecular dynamics, ab-initio calculations, topological constraints theory

Granted thesis: approx. 2350 €/month net (including social insurance)

Date of start: October 2017.

How to apply: Half of the funding has already been obtained from the ILL. To secure the other half, the candidate needs to apply to one of UPMC’s doctoral school (early may 2017, details will be given by email).

Interested candidates should send a CV and a letter of motivation to:

    Guillaume Ferlat: Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.                            

    Matthieu Micoulaut: Cette adresse e-mail est protégée contre les robots spammeurs. Vous devez activer le JavaScript pour la visualiser.