Entropy versus energy: The phase behavior of a hard-disk mixture in a periodic external potential

Abstract

The phase behavior of a 50% binary hard-disk mixture with diameter ratio sigmaB/sigmaA=0.414 , which is exposed to a one-dimensional periodic potential, is examined via Monte Carlo simulations. We find an induced structural crossover in the modulated liquid. At higher densities, depending on the strength of the external potential, the system exhibits a tunable demixing transition, followed by fluid-solid coexistence of an equimolar mixture with the S1(AB) square lattice. We find a decoupled melting of the sublattices of the S1(AB) lattice. The melting of the small-component sublattice perpendicular to the external potential minima leads to fissuring in the large-component sublattice.