Field-theoretic approach to ionic systems: Criticality and tricriticality

✍ Scribed by A Ciach; G Stell

• Book ID: 104303309
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 889 KB
• Volume: 87
• Category: Article
• ISSN: 0167-7322
• DOI: 10.1016/s0167-7322(00)00125-2

✦ Synopsis

A Landau-Ginzburg functional of two order parameters (charge-density ¢ and massdensity deviation ~?) is developed in order to yield a field theory relevant to ionic lattice gases as well as a family of off-lattice models of ionic fluids that go beyond the restricted primitive model (RPM). In a mean-field (MF) approximation an instability of a uniform phase with respect to charge fluctuations with a wave-number k =fi 0 is found. This secondorder transition to a charge-ordered phase terminates at a tricritical point (tcp). Beyond MF, a singularity of a mass correlation function for k --+ 0 occurs at ion concentration lower than that of the MF tcp. An effective functional depending only on r~ is constructed. For low ion concentration the usual Landau form of the simple-fluid (Ising) functional is obtained; hence in this theory the critical point is in the Ising universality class.