Abstract
While molecular dynamics (MD) has proven to be a promising approach to investigate the diffusion properties, the grand challenge resides in evaluating potential model parameters to accurately replicate experimentally measured properties. The Buckingham potential model with Columbic interaction is widely employed in MD simulations of chromia (Cr2O3) systems, as it allows for reasonable computational cost and accuracy. However, considering the well-known limitation of classical potential models in simultaneous reproduction of various physical phenomena, further comprehensive evaluation of the potential is required for calculation of diffusion properties. In this study, we benchmark the performance of three different Buckingham models with the experimental data by calculating structural, thermodynamic, and mechanical properties of defect-free Cr2O3, and diffusion properties of Cr2O3 with vacancy defects. Available Buckingham models display limited accuracies, consolidating the necessity of retraining the potential parameters for all properties impacting the diffusion dynamics. Oversimplification in parameterization procedures is suggested to impede the universal performance in property reproduction. This research also demonstrates effective guidelines for choosing a proper parameter set of current Buckingham potential for MD simulation with Cr2O3 depending on properties and for potential reparameterization.
Highlights
Chromia (Cr2O3) is a well-known oxidation- and corrosionresistant coating, which is formed at high temperatures and protects metallic alloys in various aqueous and gaseous surroundings.1–7 To elucidate the formation mechanism of chromia scale and the defect-dependent properties, such as thermal and electrical conductivities,5 a quantitative understanding of the corresponding self-diffusion kinetics of vacancy, interstitial, and grain boundary is necessary
The Buckingham model with the Columbic interaction has been widely employed in Molecular dynamics (MD) simulations of Cr2O3 systems,14,21,22 as it allows for reasonable computational cost and accuracy, but further comprehensive evaluation of the potential is required for calculation of diffusion properties
Differing from other properties, MD simulation for diffusion kinetics is sensitive to a simulation domain dimension and time scale, and sufficiently large cell size and time scale are essential to obtain reliable diffusion properties via MD
Summary
Chromia (Cr2O3) is a well-known oxidation- and corrosionresistant coating, which is formed at high temperatures and protects metallic alloys in various aqueous and gaseous surroundings. To elucidate the formation mechanism of chromia scale and the defect-dependent properties, such as thermal and electrical conductivities, a quantitative understanding of the corresponding self-diffusion kinetics of vacancy, interstitial, and grain boundary is necessary. The reported experimental self-diffusion coefficients span over a wide range (10-22 - 10-11cm2/s); it is very challenging to examine the atomic-scale diffusion mechanisms inside the Cr2O3 from experiments. With recent advances in accelerating algorithms and computing power, temporal and spatial scale of MD simulations are significantly extended (up to microsecond and millions of atoms, respectively) for more accurate diffusion predictions. Despite these advantages of MD approach, not all diffusion processes in Cr2O3 have been studied (e.g., grain boundary diffusion has not been reported, according to the best knowledge of the authors) and further improvement is required in MD study
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