title: Penetrable square-well fluids: exact results in one dimension.
abstract: We introduce a model of attractive penetrable spheres by adding a short-range attractive square well outside a penetrable core, and we provide a detailed analysis of structural and thermodynamical properties in one dimension using the exact impenetrable counterpart as a starting point. The model is expected to describe star polymers in regimes of good and moderate solvent under dilute conditions. We derive the exact coefficients of a low-density expansion up to second order for the radial distribution function and up to fourth order in the virial expansion. These exact results are used as a benchmark to test the reliability of approximate theories (Percus-Yevick and hypernetted chain). Notwithstanding the lack of an exact solution for arbitrary densities, our results are expected to be rather precise within a wide range of temperatures and densities. A detailed analysis of some limiting cases is carried out. In particular, we provide a complete solution of the sticky penetrable-sphere model in one dimension up to the same order in density. The issue of Ruelle's thermodynamics stability is analyzed and the region of a well-defined thermodynamic limit is identified.
authors.affiliation: Departamento de Física, Universidad de Extremadura, E-06071 Badajoz, Spain. andres@unex.es
authors.forename: Andrés
authors.initials: A
authors.lastname: Santos
authors.forename: Riccardo
authors.initials: R
authors.lastname: Fantoni
authors.forename: Achille
authors.initials: A
authors.lastname: Giacometti