Microscopic structure and thermodynamics of a core-softened model fluid: Insights from grand canonical Monte Carlo simulations and integral equations theory

Abstract

We have studied the microscopic structure and thermodynamic properties of isotropic three-dimensional core-softened model fluid by using extensive grand canonical Monte Carlo computer simulations and Ornstein-Zernike integral equations with hypernetted chain and Rogers-Young closures. Applied simulation tools permit to obtain insights into the properties of the model in addition to available molecular dynamics data of other authors. We discuss equation of state in the density-chemical potential projection and explore the temperature dependence of the chemical potential along different isochores. The limits of the region of anomalous behavior of the structural and thermodynamic properties are established by investigating derivatives resulting from the equation of state, pair contribution to excess entropy, and translational order parameter. Besides, we evaluate the dependence of the heat capacity on temperature and density. The microscopic structure is discussed in terms of the pair distribution functions and corresponding structure factors. We have established that the hypernetted chain approximation is not successful to capture the region of anomalies in contrast to Rogers-Young approximation, but is very accurate for high fluid densities. Thus we have studied the onset for crystallization transition within this theoretical framework. Moreover, using the replicated Ornstein-Zernike integral equations with hypernetted chain closure, we explore the possibility of glass transition and described it in terms of transition density and chemical potential.