TY - JOUR

T1 - Role of vacancies in structural thermalization of binary and high-entropy alloys

AU - Kristoffersen, Henrik H.

AU - Pedersen, Jack K.

AU - Rossmeisl, Jan

N1 - Funding Information: The authors acknowledge support from the Danish National Research Foundation Center for High-Entropy Alloy Catalysis (CHEAC) DNRF-149. Publisher Copyright: © 2023 The Author(s)

PY - 2023

Y1 - 2023

N2 - Vacancy assisted atomic self-diffusion is a major structural thermalization mechanism in bulk metal alloys. Depending on alloy composition, the local atomic environments might stabilize vacancies to such extent that the vacancies become trapped and the atomic self-diffusion part of the thermalization process stalls. The consequence is that such alloys get kinetically trapped in disordered structures. In this study, we investigate equimolar AgAu, CuPt, AgPdPtIr, and AgAuCuPdPt alloy thermalizing using Metropolis Monte Carlo simulations in two approaches, one where the alloy structure changes through vacancy migration and one where the structure changes by swapping atomic pairs. By comparing the two approaches, we find that the vacancy is less effective at thermalizing alloys with more elements (i.e. AgPdPtIr and AgAuCuPdPt), more heterogeneous configurational internal energy distributions (i.e. CuPt and AgPdPtIr), and strong interactions between certain elements, e.g. Ir-Ir interactions in AgPdPtIr. In the case of AgPdPtIr, the vacancy cannot thermalize Ir-Ir neighbors even when the vacancy is mobile, because the vacancy has difficulty breaking individual Ir-Ir pairs apart.

AB - Vacancy assisted atomic self-diffusion is a major structural thermalization mechanism in bulk metal alloys. Depending on alloy composition, the local atomic environments might stabilize vacancies to such extent that the vacancies become trapped and the atomic self-diffusion part of the thermalization process stalls. The consequence is that such alloys get kinetically trapped in disordered structures. In this study, we investigate equimolar AgAu, CuPt, AgPdPtIr, and AgAuCuPdPt alloy thermalizing using Metropolis Monte Carlo simulations in two approaches, one where the alloy structure changes through vacancy migration and one where the structure changes by swapping atomic pairs. By comparing the two approaches, we find that the vacancy is less effective at thermalizing alloys with more elements (i.e. AgPdPtIr and AgAuCuPdPt), more heterogeneous configurational internal energy distributions (i.e. CuPt and AgPdPtIr), and strong interactions between certain elements, e.g. Ir-Ir interactions in AgPdPtIr. In the case of AgPdPtIr, the vacancy cannot thermalize Ir-Ir neighbors even when the vacancy is mobile, because the vacancy has difficulty breaking individual Ir-Ir pairs apart.

KW - Ab initio calculations

KW - Atomistic simulations

KW - Computational thermodynamics

KW - Out of equilibrium modeling

KW - Theory and modeling (kinetics, transport, diffusion)

U2 - 10.1016/j.actamat.2023.119398

DO - 10.1016/j.actamat.2023.119398

M3 - Journal article

AN - SCOPUS:85172888533

VL - 261

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

M1 - 119398

ER -