Crossover behavior in fluids with Coulomb interactions

Oksana Patsahan (1) , Jean-Michel Caillol (2) , Ihor Mryglod (1)

1 ICMP - Institute for Condensed Matter Physics of NAS of Ukraine
2 LPT - Laboratoire de Physique Théorique d'Orsay [Orsay]

According to extensive experimental findings, the Ginzburg temperature $t_{G}$ for ionic fluids differs substantially from that of nonionic fluids [Schröer W., Weigärtner H. (2004) Pure Appl. Chem. 76 p.19]. A theoretical investigation of this outcome is proposed here by a mean field analysis of the interplay of short and long range interactions on the value of $t_{G}$. We consider a quite general continuous charge-asymmetric model made of charged hard spheres with additional short-range interactions (without electrostatic interactions the model belongs to the same universality class as the $3D$ Ising model). The effective Landau-Ginzburg Hamiltonian of the full system near its gas-liquid critical point is derived from which the Ginzburg temperature is calculated as a function of the ionicity. The results obtained in this way for $t_{G}$ are in good qualitative and sufficient quantitative agreement with available experimental data.

Domaines: Mécanique statistique [cond-mat.stat-mech]

Oksana Patsahan, Jean-Michel Caillol, Ihor Mryglod. Crossover behavior in fluids with Coulomb interactions. 2007. ⟨hal-00139998⟩