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Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

preprint
revised on 20.01.2021, 20:07 and posted on 21.01.2021, 13:11 by Stephen T. Lam, Qing-Jie Li, Ronald Ballinger, Charles Forsberg, Ju Li

Lithium-based molten salts have attracted significant attention due to their applications in energy storage, advanced fission reactors and fusion devices. Lithium fluorides and particularly 66.6%LiF-33.3¾F2 (Flibe) are of considerable interest in nuclear systems, as they show an excellent combination of desirable heat-transfer and neutron-absorption characteristics. For nuclear salts, the range of possible local structures, compositions, and thermodynamic conditions presents significant challenges in atomistic modeling. In this work, we demonstrate that atom-centered neural network interatomic potentials (NNIP) provide a fast and accurate method for performing molecular dynamics of molten salts. For LiF, these potentials are able to accurately model dimer interactions, crystalline solids under deformation, semi-crystalline LiF near the melting point and liquid LiF at high temperatures. For Flibe, NNIPs accurately predicts the structures and dynamics at normal operating conditions, high temperature-pressure conditions, and in the crystalline solid phase. Furthermore, we show that NNIP-based molecular dynamics of molten salts are scalable to reach long timescales (e.g., nanosecond) and large system sizes (e.g., 105 atoms), while maintaining ab initio accuracy and providing more than three orders of magnitude of computational speedup for calculating structure and transport properties.

Funding

Natural Sciences and Engineering Research Council

Natural Sciences and Engineering Research Council

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Shanghai Institute of Applied Physics

Department of Energy, Office of Nuclear Energy, Nuclear Energy University Program (NEUP), Award Number DE-NE0008751

History

Email Address of Submitting Author

stephen_lam@uml.edu

Institution

University of Massachusetts Lowell

Country

United States

ORCID For Submitting Author

0000-0002-7683-1201

Declaration of Conflict of Interest

no conflict of interest

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