NEGATIVE THERMAL-EXPANSION OF THE ONE-DIMENSIONAL LATTICE GAS WITH HARD-CORE NEAREST-NEIGHBOR AND NEXT-NEAREST-NEIGHBOR INTERACTIONS

A one-dimensional lattice gas model with the hard-core nearest-neighbor and the next-nearest neighbor interactions is exactly solved. The Helmholtz free energy is given in explicit expression of proper thermodynamic variables, the temperature and the number density. In the case of repulsive next-nearest-neighbor interaction, the coefficient of thermal expansion has a negative region, and hence there is an intersection of isotherms and a maximum number density as a function of temperature in constant pressure process.