Re: Regarding applying dipole-dipole moment on dimer particles

[Martin Kaiser]

Dear Chandra,

I am lacking a bit of detail to understand the exact set-up of your system so I'll try to give a general answer. 

A dipole moment is added to a particle with the “dipm” or “dip” parameters at the set up of the particle. You can check this out in the documentation in chapter 9: https://espressomd.org/html/doc4.1.4/magnetostatics.html. With “dipm” you can set the magnitude of the point dipole, with “dip” you can set the components of the vector directly.

If you have decided on a solver (P3M is a good choice in periodic 3 dimensional systems), all particles that have either “dipm” or “dip” parameters will interact via the dipole-dipole potential. Bare in mind that it is not enough to just assign a dipole moment to the particles, but you must explicitly add magnetic interactions to the actors in your script, for example:

import espressomd.magnetostatics as magnetostatics
p3m = magnetostatics.DipolarP3M(prefactor=1, mesh=32, accuracy=1E-4)
system.actors.add(p3m)

Again, the documentation has all the info that you need if paired with the tutorials.

Since dipoles are point-dipoles, they don’t have a “surface” in that sense. I suppose what you want to use is the “raspberry-model”, of which there is detailed literature and a dedicated espresso-tutorial. This allows you to distribute dipoles on the surface and in the center of the particle, if that’s what you are going for.

Best,

Martin

On 28.12.2020, at 14:59, chandra shekhar maurya <chandra15294@gmail.com> wrote:

Dear users,

I have created  dimer particles, and am trying to apply dipole-dipole moment on each particle (center+surface) using tutorial 11-ferrofluid_part1. But i am unable to do this. How can I apply dipole moment on both particles (center+surface) ?

Can anyone help me?

Your help will be highly appreciated.

Thanks & Regards

Chandra Shekhar Maurya

Mechanical Eng. Dept.

Indian Institute of Technology Patna

Contact No:9793572837