Microcanonical Monte Carlo simulation of lattice gas models.

We introduce a true microcanonical ensemble appropriate for Monte Carlo simulations of lattice gas models in which both the energy and the number of particles are held fixed. We also deduce formulas that allow us to do the calculation of the intensive quantities: temperature and chemical potential. The numerical results coming from Monte Carlo simulations defined according to this microcanonical ensemble compare well with results coming from the ordinary canonical ensemble.