Abstract
In this work, we present a phase-field model that captures the evolution of ionic concentrations and phase fractions during solid-state metathesis (SSM) reactions where diffusion limits the rate of transformation. The evolution of the mole fraction of each ion is obtained via governing equations that describe the reduction of a free energy, which includes an energy landscape with local minima located at compositions corresponding to stable products. We utilized two Lagrange multipliers to impose constraints of electroneutrality as well as on the sum of mole fractions, which were then eliminated to derive set of two partial differential equations that describe the dynamics of the mole fraction evolution. From these governing equations, the expressions for effective mobilities for the cations and the anions were obtained. We first study the effect of mobilities of ions on the reaction kinetics, using a simple model considering the ions with an identical absolute value of charge numbers. The simulation results show that the overall characteristic mobility, defined as the sum of the two effective ionic mobilities, provides an excellent measure of the rate at which reaction progresses and that the ratio of the effective mobilities of the anions and the cations signifies the manner by which the reaction progresses. We then generalize the model to consider ions with different charge numbers and tuned the mobility of ions based on their diffusion coefficients reported in the literature and experimental data from a thin-film experiment for the synthesis of FeS2 to demonstrate the capability of the model to predict the phase evolution during SSM reactions. In particular, the simulation predicts nonplanar phase evolution, which is recently observed in thin-film reactions for the synthesis of FeS2 via transmission electron microscopy. The approach can serve as a basis for models for phase transformations in other multiphase ionic mixtures, such as in all-solid-state batteries and in ionic liquids.
Original language | English |
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Article number | 112080 |
Journal | Computational Materials Science |
Volume | 221 |
DOIs | |
State | Published - Mar 25 2023 |
Funding
This work was supported as part of GENESIS: A Next Generation Synthesis Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under award No. DE-SC0019212. The computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231, and the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede2 at the TACC through allocation No. TG-DMR110007, which is supported by National Science Foundation grant number ACI-1548562. The research utilized experimental data obtained at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725. Finally, the authors would like to thank Vikram Gavini for the useful discussion. This work was supported as part of GENESIS: A Next Generation Synthesis Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under award No. DE-SC0019212. The computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231, and the Extreme Science and Engineering Discovery Environment (XSEDE) Stampede2 at the TACC through allocation No. TG-DMR110007, which is supported by National Science Foundation grant number ACI-1548562. The research utilized experimental data obtained at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725. Finally, the authors would like to thank Vikram Gavini for the useful discussion.
Funders | Funder number |
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Extreme Science and Engineering Discovery Environment | |
TACC | TG-DMR110007 |
Vikram Gavini | |
XSEDE | |
National Science Foundation | ACI-1548562 |
U.S. Department of Energy | |
Office of Science | |
Basic Energy Sciences | DE-SC0019212 |
Oak Ridge National Laboratory | |
Lawrence Berkeley National Laboratory | DE-AC02-05CH11231 |
UT-Battelle | DE-AC05-00OR22725 |
Keywords
- Diffusion
- Ionic compounds
- Lagrange multiplier
- Metathesis reaction
- Phase-field model