Atom fixed but finding its velocity update

Submitted by mofazli on Thu, 12/02/2021 - 09:08

Hi everyone,
I hope you are all well.
I have a question about Liggghts ability to fix the particles in their position but update their velocities. We know liggghts has the following command:
fix 3 wall nve/noforce
which does the opposite thing I need, changing particles position but fixing their velocity. I need to keep the particles in their initial position, but update their velocities based on forces. Now I am using the following command:
fix integr all nve/sphere
which updates both positions and velocities. So can anyone help me with answering this question?
Cheers,
Mohammad

Forums:

mofazli | Fri, 12/03/2021 - 00:17

JFYI, I fixed the particles but updated velocity through commenting the lines 173-175 in fix_nve_sphere.cpp:
// position update
x[i][0] += dtv * v[i][0]; //Insert by Mo
x[i][1] += dtv * v[i][1]; //Insert by Mo
x[i][2] += dtv * v[i][2]; //Insert by Mo