[lammps-users] Strange: Why the atoms do not move?

Dear All, I set following commands in order to move the group of atoms in some velocity downward z direction,

velocity test set NULL NULL -9.0 sum yes units box
timestep 0.001
run 1000

I recorded the coordinates of center of mass every 50 steps. It is expected the Z component of com should decrease regularly.

But it seems that the possition of center of mass does not change at all. Why? Did I missed some other commands to trigger the translational motion?

Thanks.

Dear All, I set following commands in order to move the group of atoms in
some velocity downward z direction,

velocity test set NULL NULL -9.0 sum yes units box
timestep 0.001
run 1000

I recorded the coordinates of center of mass every 50 steps. It is expected
the *Z* component of com should decrease regularly.

But it seems that the possition of center of mass does not change at all.
Why? Did I missed some other commands to trigger the translational motion?

dear jarvis,

nobody can tell for certain what is going wrong, if you don't
provide functional input scripts. posting only input fragments
forces people to guess or may even make it impossible to give
a useful answer at all.

my first guess would be that you forgot to actually propagate
atoms, i.e. didn't use one of the ensemble fixes.

cheers,
   axel.

fix 1 all nve

2009/1/4 Jarvis Chong <[email protected]…24…>

Dump the coords and velocities every step - are they what you
expect?

Steve