Two-stage melting in tribological systems

A melting phase transition in a thin lubricant film confined between two substrates in moving contact is considered. General theoretical arguments are usually used to prove that ordinary bulk melting is always a first-order phase transition. However, this is not the case for systems with static and dynamic asymmetries. It is shown theoretically that a given tribological system can exhibit a novel two-stage continuous second-order transition, which is confirmed by a Langevin molecular dynamics study.