Features of Phase Transitions in Models of Complex Plasma

Abstract

AbstractSome features of melting curves and fluid‐crystal phase transitions in complex plasmas are under discussion. The base for a consideration is the well‐known phase diagram of dusty plasma (Hamaguchi, 1997) for an equilibrium charged system with the Yukawa potential in Γ − κ plane (Γ is the Coulomb non‐ideality parameter,κ is a screening parameter). This phase diagram is converted for a one‐component Yukawa system in ordinary density ‐ temperature plane. A melting curve is converted for this system in temperature ‐ pressure plane. There are some density gap estimations based on a hypothesis of similar melting properties in Yukawa systems and Soft Spheres systems. The initial phase diagram is also converted for two one‐temperature models of complex plasmas in density – temperature plane. Here simplified variants of complex plasmas models are considered as a thermodynamically equilibrium ensemble of classical Coulomb particles: a 2‐component electroneutral system of macro‐ and microions (+Z, −1) and a 3‐component electroneutral mixture of macroions and two kinds of microions (+Z, −1, +1). The resulting phase diagram for (+Z,−1) or (−Z,+1) in ln n − ln T plane has a form of a linear combination of crystalline and fluid zones separated by the boundaries Γ = const. Parameters and locations of these zones are analyzed in dependence on macroion charge number Z. There are huge negative pressure and negative compressibility areas in the initial phase diagram if one uses equations of state (Hamaguchi,1997) and (Khrapak, 2014). Thus, questions of thermodynamic stability and an existence of an additional phase transition gas‐liquid are discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)