Eur. Phys. J. D 18, 339-345 (2002)
https://doi.org/10.1140/epjd/e20020039

Systematic field-theory for the hard-core one-component plasma

¹ Max-Planck-Institute of Colloids and Interfaces, 14424 Potsdam, Germany
² Moscow State University, Physics Department, Moscow 119899, Russia
³ Sektion Physik, Ludwig-Maximilians-Universität, Theresienstr. 37, 80333 München, Germany

Corresponding author: ^a netz@mpikg-golm.mpg.de

Received: 18 June 2001
Revised: 4 October 2001
Published online: 15 March 2002

Abstract

An accurate and systematic equation of state for the hard-core one-component plasma (HCOCP) is obtained. The result is based on the Hubbard-Schofield transformation which yields the field-theoretical Hamiltonian, with coefficients expressed in terms of equilibrium correlation functions of the reference hard-core fluid. Explicit calculations were performed using the Gaussian approximation for the effective Hamiltonian and known thermodynamic and structural properties of the reference hard-core fluid. For small values of the plasma parameter Γ and packing fraction the Debye-Hückel result is recovered, while for , the excess free energy F_ex and internal U_ex energy depend linearly on Γ. The obtained expression for U_ex is in a good agreement with the available Monte Carlo data for the HCOCP. We also analyse the validity of the widely used approximation, which represents the free energy as a sum of the hard-core and electrostatic part.