Why nve and nvt are used in shear script

Dear LAMMPS users,

I¡¯m making grain boundary sliding simulation using LAMMPS.

So, I want to use addforce command for shear stress.

I have looked for scripts about shear stress and known that fix nve and nvt command are used in many scripts.

But I don¡¯t know why nve and nvt command are used¡¦

Please let me know about this.

I¡¯m sorry that English is poor.

Dear LAMMPS users,

I’m making grain boundary sliding simulation using LAMMPS.

So, I want to use addforce command for shear stress.

I have looked for scripts about shear stress and known that fix nve and nvt command are used in many scripts.

But I don’t know why nve and nvt command are used…

Please let me know about this.

Fix nve defines a simple velocity verlet time integrator that just integrates forces in time.
Fix nvt defines a velocity verlet integrator with No sé-Hoover thermostatting so that the temperatures is constant.

If no other fixes are defined and the boundary conditions are periodic, then nve will sample the microcanonical ensemble and NVT will sample the canonical ensemble.

I think either of them is needed in order to make sure the motion caused by the moving boundary is propagated throughout the material.

I’m sorry that English is poor.

No worries.