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arXiv · 2605.01863

Surface segregation of liquid metal plasma-facing component alloys: A ReaxFF investigation

Md Adnan Mahathir Munshi·Abdul Aziz Shuvo·Mike Kotschenreuther·Adri C. T. van Duin·Bladimir Ramos-Alvarado
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Abstract

Engineering liquid metal alloys offers a transformative pathway for plasma-facing components (PFC) by enabling chemically tailored surfaces that can simultaneously optimize plasma-material interactions, reduce divertor heat flux, and enhance core plasma confinement, thereby advancing the commercial viability of nuclear fusion power plants. This study, employing an atomistic simulation framework, provides direct evidence that incorporating non-metal surface-active agents (such as O and H, or their combination) enables strong surface segregation. This capability makes tin-aluminum (Sn-Al) and tin-lithium (Sn-Li) alloys, with suitable compositions, good candidates for PFC applications. Specifically, the presence of low-Z solutes (Li, Al) leads to preferential surface enrichment, which imparts low-Z sputtering characteristics, while the Sn solvent maintains thermophysical stability. To systematically examine this behavior, we first optimized ReaxFF parameter sets for Sn-Al, Sn-Al-O, Sn-Li, Sn-Li-O, Sn-Li-H, and Sn-Li-O-H systems. We validated them using formation energies and elastic constants. We then employed reactive molecular dynamics simulations to resolve the coupled effects of surface segregation and impurity-driven chemistry at fusion-relevant temperatures. We also introduced an overlap-based segregation index that captures interfacial compositional separation directly from atomistic density distributions. This metric reveals a clear hierarchy of segregation regimes across all systems and presents a unified view of segregation across all observations reported herein. Together, these findings establish a mechanistic link between non-metal chemistry and interfacial structure, providing a predictive framework for designing self-adaptive, low-sputtering liquid metal alloys for fusion applications.

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Md Adnan Mahathir Munshi, Abdul Aziz Shuvo, Mike Kotschenreuther, Adri C. T. van Duin, Bladimir Ramos-Alvarado. 2026-05-03. Surface segregation of liquid metal plasma-facing component alloys: A ReaxFF investigation. https://arxiv.org/abs/2605.01863

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