Swap Monte Carlo for diatomic molecules

Abstract: In recent years the Swap Monte Carlo algorithm has led to remarkable progress in equilibrating supercooled model liquids at low temperatures. Applications have so far been limited to systems composed of spherical particles, however, whereas most real-world supercooled liquids are molecular. We here introduce a simple size-polydisperse molecular model that allows for efficient thermal equilibration \textit{in silico} with the Swap Monte Carlo method, resulting in an estimated speedup of $10^3-10^6$ at moderate polydispersity (5-10 %). Despite being polydisperse, the model exhibits little difference between the size-resolved orientational time-autocorrelation functions. Our results demonstrate the possibility of designing molecular models that can be simulated close to the calorimetric glass transition.