Group was applied a Langevin thermostat to maintain temperature and a normal force to move it down in z direction.
With larger damp, it was moved faster.
With smaller damp, it was moved slower.
I think damp only affects with temperature, not with velocity. But it does.
Anyone has suggestions?
Are you thermostating and apply an external force to the same group of atoms? If yes, then the thermostat will equilibration the group and neutralize the force.
What you observed is expected: larger damp value, weaker damping, slower the neutralization, hence the atoms moved faster. The opposite is also true.
Bottom line: remove the thermostat on the group.
If you thermostat a group of atoms
moving collectively, then the thermostat
will affect the collective motion. Unless
you remove the collective velocity before
thermostatting. In LAMMPS that is called
removing a bias and there are several
temperature computes that do it in different ways. See
Section 6.16 of the doc pages for an overview.
compute myTemp group temp/profile 1 1 1 xyz 1 1 1
fix 3 group langevin 300.0 300.0 10.0 699483
fix_modify 3 temp myTemp
Is that right?
Many Refs applied both on the same group.
You’ll have to try it yourself, see
what it does, use your script and output
to debug what it is doing, read the doc
pages carefully. Asking the
mail list for reassurance is not a substitute