A simulation study of the quantum hard-sphere Yukawa fluid

Abstract

The quantum hard-sphere fluid with attractive Yukawa interactions is studied along several isochores, at low and medium densities, by varying the rest of the parameters that define its state points (the temperature, and the well-depth and inverse range of the attractive tail). Path integral Monte Carlo simulations are performed to fix the thermodynamics (energies and pressures) and the pair structures in r-space (instantaneous, linear response, and centroids). The k-space structure factors associated with these radial structures are determined via direct correlation functions defined by suitable Ornstein–Zernike equations. The results obtained allow one to assess quantitatively the reduction in the quantum features of the hard-sphere system due to the inclusion of attractive interactions. Besides, it is observed that under certain conditions the Yukawa interactions can lead to the formation of cavities in the system. For the sake of comparison, some complementary simulations of the bare quantum hard-sphere system have also been carried out, which have helped to resolve certain unclear features near a fluid–solid change of phase of this system. At the onset of increasing fluctuations in the Yukawa system one can observe, from the computation of k-space properties, the negligible role of the repulsive forces in this issue, and also the direct correlation function features associated with the attractions. In addition, the current quantum results give evidence of the decrease in both the critical temperature and the critical density of the Yukawa system, as compared with its classical counterpart.