Polar hard dumb-bells and a RISM model for water

Abstract
The solution of the RISM equation for polar hard dumb-bells (PHD) within the mean spherical approximation is presented. The dielectric constant for a fluid of such molecules is found to be given by ε=1+3y. A charged tetrahedral RISM molecule is proposed as a simple model for water. The solution of the RISM equation for this molecule and the dielectric constant are also obtained.