Re: Regarding applying dipole-dipole moment on dimer particles

[Martin Kaiser]

I have just seen your last mails to the list stating that you use the raspberry model. In that case you can ignore the last paragraph of my last answer and stick just to the rest: Assign “dip” to all particles that you want to magnetically interact and then add a solver to the actors in your script.

Best,

Martin

On 28.12.2020, at 15:37, Martin Kaiser <martin.kaiser@univie.ac.at> wrote:

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