Abnormal kinetic-energy fluctuations and critical behaviors in the microcanonical lattice gas model

In this paper we present a microcanonical lattice gas model with a fluctuating volume. In the first-order liquid-gas phase transition region thermodynamical anomalies such as a back-bending in the caloric curve and a negative heat capacity are observed. This phenomenon induces abnormal kinetic-energy fluctuations and is associated with a critical fragment size distribution. The relevance of these findings for the experimental detection of a liquid-gas phase transition in finite systems is discussed.