Phase separation in two-dimensional additive mixtures

CNRS, Laboratoire de Physique Statistique, Ecole Normale Supe´rieure, 24, rue Lhomond, 75231 Paris Cedex 05, France~Received 2 July 1998; revised manuscript received 4 November 1998!We study two-dimensional binary mixtures of parallel hard squares as well as of disks. A recent clusteralgorithm allows us to establish an entropic demixing transition between a homogeneously packed fluid phaseand a demixed phase of a practically close-packed aggregate of large squares surrounded by a fluid of smallsquares. @S1063-651X~99!00803-X#PACS number~s!: 61.20.Gy, 64.75.1g