velocity command

Dear Lammps users

I want to pull a set of atom off of a surface (in z-dir) by a constant velocity (of course I want the surface to not move)
I used below recipe

group pull id 409
group surf molecule 1
fix 2 surf spring/self 100.0 z

velocity pull set NULL NULL 1.00 sum yes units box
fix 1 all nvt temp 298.15 298.15 100.0

but I don’t see any upward movement of atom 409
Am I doing anything wrong?

Thanks

Dear Lammps users

I want to pull a set of atom off of a surface (in z-dir) by a constant
velocity (of course I want the surface to not move)
I used below recipe

group pull id 409
group surf molecule 1
fix 2 surf spring/self 100.0 z
velocity pull set NULL NULL 1.00 sum yes units box
fix 1 all nvt temp 298.15 298.15 100.0

but I don't see any upward movement of atom 409
Am I doing anything wrong?

the velocity command will just set the *initial*
velocity. you have to set all its forces to zero
*and* integrate it with fix nve (instead of fix nvt)
to have it move at a constant velocity.

it would be easier to use fix move instead.

axel.