Programme

I.13 -- Invited, VCTP-44

Date: Thursday, 1 August 2019

Time: 16:00 - 16:30

Predictive modelling of steady-state configuration in non-equilibrium physics

Duc Nguyen-Manh

Department of Materials Science and Scientific Computing, CCFE, United Kingdom Atomic Energy Authority, Abingdon OX14 3DB, UK

Nuclear fusion offers the potential of predictable, safe power with no carbon emissions and fuel sources lasting for millions of years. However, it is notoriously difficult to achieve in a controlled, steady-state fashion. A magnetic confinement nuclear fusion power plant requires many different science (including theoretical physics), technology and engineering challenges to be met simultaneously. An integrated approach from the outset is needed to bring fusion electricity closer if the other challenges are resolved in harmony.
In this talk, a recent breakthrough in predicting steady-state solution of the phase stability under strong irradiation in multiple-component systems as plasma-facing materials for fusion devices is presented. The work has been carried out within an international collaboration between the UKAEA leading modelling team and different experimental groups at Los Alamos National Laboratory, Argonne National Laboratory and Pacific Northwestern National Laboratory (USA) in finding outstanding radiation resistance materials based on W-based so-called high-entropy alloys (HEAs) [1]. Our theoretical work is developed by using the constrained thermodynamic formalism combining ab-intio construction of many-body Hamiltonian to model for to model K-component alloy system under irradiation for which irradiated defects are being considered as the additional elements in the system. It is found that the formalism can be mathematically respresented within matrix formulation for the K-component alloys via many-body cluster correlation functions which in turn can be computed efficiently from Monte-Carlo simulations in a combination with first-principles cluster-expansion Hamiltonian [2]. Applying the theory for bcc W-Ta-Cr-V based HEAs, it is predicted that there is a strong phase decomposition between W, Ta and Cr, V as a function of composition and temperature. The formation of Cr and V rich phase found from the MC simulations is in an excellent agreement with the precipitates observed with Atom Probe Tomography analysis for W 38 Ta 36 Cr 15 V 11 alloy irradiated at high temperatures. The competition between phase segretation and radiation effects is discussed to understand the origin of observed outstanding radiation resistance.
[1] O. El-Atwani, N. Li, M. Li, A. Devaraj, J. K. S. Baldwin, M. M. Schneider, D. Sobieraj, J. S. Wróbel, D. Nguyen-Manh, S. A. Maloy, E. Martinez, Science Advances, 5 (2019) eaav2002
[2] A. Fernandez-Caballero, M. Fedorov, J.S. Wrobel, P.M. Mummery, D. Nguyen-Manh, Entropy, 21 (2019) 00068

Presenter: Nguyen Manh Duc