January 7th, 2026

Can a system as thoroughly studied as the Lennard-Jones gas still reveal intriguing phenomena? In a collaboration with the Laboratoire de Physique de la Matière Condensée published in Phys Rev Letters, we employed Molecular Dynamics (MD) simulations and rare-event sampling to investigate liquid nucleation from the vapor phase. Contrary to the predictions of Classical Nucleation Theory, our results demonstrate that critical clusters nucleate at a density significantly different from that of the macroscopic equilibrium liquid. We rationalize these numerical findings using a two-variable nucleation theory that is both accessible and highly effective.