Authors: Hao Deng | Quanwen Sun | Meng Li | Zeyu Zhao | Wenjuan Bian | Bin Liu | Dong Ding
Source: Small Methods (article, 2025-07-09)
Field: Materials Science — Materials Chemistry

Atomistic Simulations of Thermal and Chemical Expansions of PrNi <sub>x</sub> Co <sub>1‐x</sub> O <sub>3‐δ</sub> Accelerated by Machine Learning Potentials The electrodes and solid-state electrolytes in protonic ceramic electrochemical cells (PCECs) experience significant lattice expansions when exposed to high steam concentrations at elevated temperatures. In this paper, phonon calculations based on a new machine learning potential (MLP) are employed to elucidate the volume expansions of the proton-conducting PrNi<sub>x</sub>Co<sub>1-x</sub>O<sub>3-δ</sub> (PNC) lattices, manifested under a combined influence of oxygen vacancies ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>V</mml:mi> <mml:mi>O</mml:mi> <mml:mrow><mml:mo>·</mml:mo> <mml:mo>·</mml:mo></mml:mrow> </mml:msubsup> <mml:annotation>${\mathrm{V}}_{\mathrm{O}}^{{\mathrm{\cdot\cdot}}}$</mml:annotation></mml:semantics> </mml:math> ) and proton uptake ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>OH</mml:mi> <mml:mi>O</mml:mi> <mml:mo>·</mml:mo></mml:msubsup> <mml:annotation>${\mathrm{OH}}_{\mathrm{O}}^{\mathrm{\cdot}}$</mml:annotation></mml:semantics> </mml:math> ) in the bulk at varying Ni/Co occupancies. It is revealed that the Ni/Co occupancy contributes to thermal and chemical expansions differently, where thermal expansions are related to Co occupancy. In contrast, chemical expansions are more closely associated with the Ni occupancy. Both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>V</mml:mi> <mml:mi>O</mml:mi> <mml:mrow><mml:mo>·</mml:mo> <mml:mo>·</mml:mo></mml:mrow> </mml:msubsup> <mml:annotation>${\mathrm{V}}_{\mathrm{O}}^{{\mathrm{\cdot\cdot}}}$</mml:annotation></mml:semantics> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>OH</mml:mi> <mml:mi>O</mml:mi> <mml:mo>·</mml:mo></mml:msubsup> <mml:annotation>${\mathrm{OH}}_{\mathrm{O}}^{\mathrm{\cdot}}$</mml:annotation></mml:semantics> </mml:math> lead to higher thermal expansions when compared to the pristine PNC. The temperature increase will negatively impact the hydration-induced chemical expansions. For combined thermal and chemical expansions, it is predicted that the strategies that boost the PCEC's electrochemical performance may harm the electrode-electrolyte interfacial stability, when the Ni occupancy is high, due to severe chemical expansions. Mitigating chemical expansions of the Ni-abundant PNC will benefit the interfacial stability. The presented computational methods for phonon calculations, based on emerging machine learning interatomic potential techniques are anticipated to have a lasting impact on future PCEC development. Electrolyte ; Chemical stability ; Lattice (music) ; Electrochemistry ; Phonon ; Thermal stability ; Materials science ; Thermal ; Thermal expansion ; Thermodynamics ; Electrode ; Chemistry ; Physical chemistry ; Condensed matter physics ; Physics Advancements in Solid Oxide Fuel Cells ; Magnetic and transport properties of perovskites and related materials ; Thermal Expansion and Ionic Conductivity