[ESPResSo] dipoles with fixed orientation

[Valera, Manuel]

Greetings to all,

I have a quick question and I was wondering if there is a way to do this in 
Espresso.

I am working with a system of spherical particles interacting with a lennard 
jones potential. The particles have an embedded dipole with a fixed orientation 
in space, i.e. all the dipoles point in the z direction and the dipole 
potential is simple

U(r,t)=mu*(1-3cos(t)^2)/r^3

where r is the separation between 2 particles and t is the angle between r and 
the z axis.

This is a long range potential that needs to be handle with either Ewald or 
other similar techniques. Espresso has a magnetostatic interaction that could 
be used in this case if there is a way to fix the orientation of the dipoles 
and suppressed the rotation.

Is there a way to use the magnetostatic potential (Equation 5.24 in the users 
guide) to accomplish this?

Thanks in advance for all your help.

cheers,
Manuel Valera