Numerical simulations of solvation in simple polar solvents The simulation model

4 NUMERICAL SIMULATIONS OF SOLVATION IN SIMPLE POLAR SOLVENTS THE SIMULATION MODEL  

The simplest simulated system is a Stockmayer fluid structureless particles characterized by dipole-dipole and Lennard-Jones interactions, moving in a box (size L) with periodic botmdary conditions. The results described below were obtained using 400 such particles and in addition a solute atom A which can become an ion of charge q embedded in this solvent. The long range nature of the electrostatic interactions is handled within the effective dielectric environment seheme. In this approach the simulated system is taken to be surrounded by a continuum dielectric environment whose dielectric constant e is to be chosen self consistently with that eomputed from the simulation. Accordingly, the electrostatic potential between any two partieles is supplemented by the image interaction associated with a spherical dielectric boundary of radius (taken equal to L/2) placed so that one of these 

Lennard-Jones, dipole-dipole, and charge-dipole potentials, given by 

The terms containing in the electrostatic potentials and are the reaction field image terms.The last term in Eq. [4.3.26] is included in the Lagrangian as a constraint, in order to preserve the magnitude of the dipole moments ( [l = J,) with a SHAKE 

Under these simulation conditions the pressure fluctuates in the range 500+100 At.The dielectric constant is computed from pine solvent simulations, using the 

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