Configurational entropy as a potential metric for empirical potential development and validation

Empirical interatomic potentials remain widely used due to their high computational efficiency. Yet their development and validation protocols typically emphasize properties that have limited sensitivity to the overall shape of the potential energy landscape (PEL) and can give rise to poor transferability to other properties. Here, we consider the configurational and vibrational entropy of liquid silicon (Si) predicted by seven widely utilized empirical potentials with a view of using these energy landscape parameters to assess potentials more broadly. Both vibrational and configurational entropy contributions are found to be remarkably sensitive to the form of the potential, revealing substantial differences in basin curvature, basin density, and overall PEL topology that are not captured by conventional fitting targets. With a view toward using this information for future potential development, we also show that the Debye-Waller parameter u2 provides a practical experimental proxy for configurational entropy through the localization model of relaxation.