[lammps-users] Question about Fix setforce

I am confused about this command:

If I want some “substrate” to be rigid by using “fix 1 substrate setforce 0 0 0”, does it mean that the velocity of the substrate is zero.
Therefore, the teperature of substrate should be Zero.

However, I want to model the interactions between some material (Say, Carbon nanotube) with high temperature (Say, 300K) with this ‘rigid’ substrate.

I first relaxed and equilibriated the nanotube for a long time to make them stable at 300K then I brought this structure to be contact with the substrate.

How can I reach the equilibrium of the whole system?
Or I just need to do some static calculation by using “minimize” command?

If we can reach equilibrium, which means the atoms in the substrate will have some velocity and would be conflict with originally setted “setforce 0 0 0”.

Btw, what is the main difference between fix rigid and fix setforce 0 0 0?

Many thanks

Setting the force to 0.0 doesn't set the velocity to 0.
If you do both then the atoms won't move. Or just don't
time integrate them. Fix rigid does a time integration
of a collection of atom (one or more rigid bodies) using
their aggregate force. It also sets their velocity. So those
are 2 different things.