Mar 16 2023


3:30 pm - 4:00 pm

Normand Mousseau
Université de Montréal, QC

Professor of Physics at Université de Montréal and Scientific Director of the Trottier Energy Institute

Normand Mousseau is a professor of physics at Université de Montréal and scientific director of the Trottier Energy Institute. He holds a Ph.D. in physics from Michigan State University and he pursued post-doctoral studies at the University of Oxford and Université de Montréal. He was a professor at Ohio University before moving to his current position in 2001.  His work focuses on the atomistic kinetics of complex materials and biomolecules, with more than 200 scientific articles. Over the years, he has developed numerous simulation methods, such as the activation-relaxation technique (ARTn) and kinetic ART (kART), for exploring the energy landscape of these materials and accessing experimental time scales.  His codes are used by tens of groups from around the world.

In parallel, he has been closely monitoring issues relating to energy and natural resources for more than a decade. He is the author of several books on the subject including “Au bout  du pétrole, tout ce que vous devez  savoir sur la crise énergétique” (2008) and “Gagner la guerre du climat. Douze mythes à déboulonner” released in 2017 at Éditions du Boréal. In 2013-2014, he co-chaired Quebec’s Commission on Energy Issues, to prepare Quebec’s updated energy policy. He is co-author of the IÉT Canada Energy Outlook series,  the second edition of which appeared in the fall of 2021. He is a founding member of the Transition Accelerator and he is a founding board member of the Canadian Institute for Climate Choice. From 2019 to 2021, he has co-led the Energy Modelling Initiative. Since May 2020, he is the scientific director of the Energy Modelling Hub, a national Canadian structured funded by NRCan.

He is also very involved in science-society communication. He intervenes regularly in the media on a wide range of topics, with between 100 and 150 interventions annually. Between 2011 and 2017, he produced and hosted the weekly popular science radio show «La Grande Équation» at Radio Ville-Marie. His most recent book, « Pandémie, quand la raison tombe maladie » was published by Éditions du Boréal in November 2020.

Title of the talk:

Entropic effects in concentrated solid solutions: the unexpected role of diffusion prefactors

Abstract: High-entropy alloys, i.e. alloys with multiple elements present in similar concentration, have attracted considerable attention since they were introduced 20 years ago. These materials present a number of unexpected properties, including higher fracture resistance, tensile strengths and, of interest here, anomalous vacancy diffusion. Although this latter property remains debated, it has been the topic of a fair number of experimental and numerical works. We revisited this problem in the light of our recent work on the origin of the compensation law (or Meyer-Neldel rule) [1], separating the role of the energy barrier and the entropic attempt frequency prefactor in the diffusion of point defects.  This study, on a FeNiCb concentrated solid solution, a simplified high-entropy alloy proxy, revealed unexpected behaviour for the entropic prefactor, which shows up to six orders of magnitude variation for the same vacancy diffusion mechanism and similar energy barrier as a function of local environment [2].  In this talk, I’ll discuss these results and present extensive kinetic ART simulations that highlight the effect of prefactor variation on the diffusion properties in this complex material.

This work was done in collaboration with Simon Gelin (now Univ. Pittsburgh), Alecsandre Sauvé-Lacoursière, (U Montréal), Joseph Lefebvre (U Montréal) and Gilles Adjenor (EDF) and Christophe Domain (EDF) with the support of NSERC and EDF.

[1] S. Gelin, A. Champagne-Ruel, N. Mousseau, Enthalpy-entropy compensation of atomic diffusion originates from softening of low frequency phonons, Nature Communications 11, 3977 (2020).
[2] A. Sauvé-Lacoursière, S. Gelin, G. Adjanor, C. Domain, N. Mousseau, Unexpected role of prefactors in defects diffusion: the case of vacancies in the 55Fe-28Ni-17Cr concentrated solid-solution alloys, Acta Materialia 237, 118153 (2022).