Evidence of double criticality in a fluid model with density-dependent interactions

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Evidence of a liquid-liquid equilibrium in simple fluids has recently been exposed for a density-dependent pair potential in the framework of a van der Waals theory. Here this double criticality is investigated by means of computer simulation, a perturbation theory, and integral equation theory. It is found that the critical point estimated from the integral equation thermodynamics is not associated with divergent correlations. To cope with these features, a special simulation procedure, based on the definition of local densities, is devised. Monte Carlo calculations confirm the existence of two critical points, in agreement with the predictions of perturbation theory.
© 2001 The American Physical Society. We acknowledge financial support from the Dirección General de Enseñanza Superior e Investigación Científica (DGESCYT) under Grants No. PB98-0673-C02-02 (N.G. A.), No. PB97-0258-C02-02 (E. L.), and No. PB97-0004-C03-03 (G. R. and C. F. T.).
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