Phase diagrams of hard-core repulsive Yukawa particles.

Abstract

We determine the phase behavior of hard spheres interacting with repulsive Yukawa (screened Coulomb) interaction using computer simulations. We study the effect of the hard-core diameter on the phase behavior of repulsive Yukawa particles by comparing our phase diagrams with that of repulsive point Yukawa particles. We show that for sufficiently high contact values of the pair potential (betaepsilon=20, 39, 81, and higher), the fluid-face-centered-cubic (fcc) solid, at high screening, the fluid-body-centered-cubic (bcc) solid and the bcc-fcc coexistence for packing fractions eta less, similar 0.5 are well described by the phase boundaries of point Yukawa particles, by employing a mapping of the point Yukawa system onto a hard-core repulsive Yukawa system. While the bcc-fcc coexistence is well described by the point Yukawa limit for eta<0.5, we find a deviation at higher eta as the hard-core repulsion favors the fcc solid for eta>/=0.5, independent of the screening. Consequently, a second triple point appears in the phase diagram in the weak screening regime. In addition, we find that all the phase coexistence regions in our phase diagrams for hard-core repulsive Yukawa system are very narrow, i.e., a small density jump in the coexisting phases.