Simple systems with unusual phase diagrams

Abstract

Abstract A theoretical study, based on the density functional formalism, is presented to investigate different aspects related to the phase diagram of simple systems. The approximation is a perturbation theory for non-uniform systems which in the uniform limit reduces consistently to the standard liquid perturbation theory. Its application to the solid phase requires the use of recently developed approximations for the correlation function of this phase. The theory is summarized and applied to a model of a mixture of colloidal particles and non adsorbing polymer which, under certain circumstances, can be regarded as a simple system. The predictions of the theory are in good agreement with computer simulations, even quantitatively. The role of the range of the attractive interaction between particles in determining the topology of the phase diagram is discussed. Special attention is paid to two issues: The stability of the liquid phase and the recently reported isostructural solid-solid transition in simple systems.