A third and fourth order perturbation theory for dipolar hard spheres

作者:Theiss Marc*; Gross Joachim
来源:Journal of Chemical Physics, 2018, 149(4): 044901.
DOI:10.1063/1.5035421

摘要

In this work, we develop and analyze a third order and a fourth order perturbation theory for non-polarizable dipolar hard spheres. The electrostatic potential is split into a short-ranged and a long-ranged part. A perturbation expansion is applied for the short-ranged potential where the contribution of higher order terms is approximated through a [2,1]-Pade approximation for the third order theory and by a [2,2]-Pade approximation for the fourth order theory. Rodgers andWeeks [J. Chem. Phys. 131, 244108 (2010)] developed the Local Molecular Field (LMF) theory for the long-ranged contribution of the electrostatic energy. The LMF theory requires the relative permittivity of the considered fluid. We apply a perturbation theory for the relative permittivity and show that the LMF is then in very good agreement with the results for the long-ranged energy from molecular simulations. The short-ranged contribution to the Helmholtz energy from the third order and from the fourth order perturbation theory is, for densities *rho <= 1 and for dipole moments of *mu(2) <= 1, in very good agreement with the data from molecular simulations. For larger dipole densities (up to *mu(2) <= 4 for *rho less than or similar to 1), we observe significantly improved results for the fourth order perturbation theory compared to the third order perturbation theory. Published by AIP Publishing.

  • 出版日期2018-7-28