Triple point of Yukawa systems

Abstract

The molecular dynamics simulations of Yukawa (i.e., screened-Coulomb) systems that were applied to the regime of weak screening in an earlier study [S. Hamaguchi, R. T. Farouki, and D. H. E. Dubin, J. Chem. Phys. 105, 7641 (1996)] are extended to the strong screening regime. Transition temperatures at the fluid-solid phase boundary and the solid-solid phase boundary are obtained as functions of the screening parameter $\ensuremath{\kappa}=a/{\ensuremath{\lambda}}_{D}$ (i.e., the ratio of the Wigner-Seitz radius $a$ to the Debye length ${\ensuremath{\lambda}}_{D}$). The resulting phase diagram also covers the triple point---the intersection of the fluid-solid and solid-solid phase boundaries---at $\ensuremath{\kappa}=4.28$ and $\ensuremath{\Gamma}=5.6\ifmmode\times\else\texttimes\fi{}{10}^{3},$ where \ensuremath{\Gamma} is the ratio of the Coulomb potential energy to the kinetic energy per particle (i.e., $\ensuremath{\Gamma}{=Q}^{2}/4\ensuremath{\pi}{\ensuremath{\epsilon}}_{0}akT,$ where $Q$ is the charge of each Yukawa particle and $T$ is the system temperature). Yukawa systems serve as models for plasmas and colloidal suspensions of charged particulates.