Unveiling the Temperature-Driven Surface Morphology Evolution of Iron-Based Intermetallics: A Molecular Dynamics Perspective

The surface morphology of the materials plays an important role in controlling their physical and chemical properties, particularly in the context of heterogeneous catalysis. Many iron-based material syntheses and catalytic reactions often occur over a broad temperature range. However, the precise impact of the temperature on the morphology evolution of these materials remains unclear. In this study, we employ molecular dynamics and thermodynamic integration to calculate the surface free energies of Fe2N, FeP, α-Fe2O3, and FeO at varying temperatures. Subsequently, we construct their Wulff shapes to investigate the impact of the temperature on surface morphology. The findings indicate that the free energies of the majority of the surface systems exhibit a pronounced decline with increasing temperature. This decrease is predominantly attributed to the entropy effect. Furthermore, the gradients of the descent curves for specific surfaces are notably steeper compared to others, a phenomenon that becomes particularly pronounced when the temperature exceeds a critical threshold. This leads to a notable alteration of surface morphology. For instance, at a temperature of 1300 K, the surface morphology of Fe2N, FeP, and α-Fe2O3 exhibits distinct characteristics compared to those observed at lower temperatures. This work provides theoretical insights for tuning the surface morphology of iron-based nanocatalysts through temperature control to potentially enhance the catalytic performance.