Dear all,
I want to allow a group of atoms to move only in z-direction.
So, I used fix/setforce command to zero the forces in x,y direction like this,
fix 4 upper setforce 0.0 0.0 NULL
However, the group translates in y direction during simulation.
In next trial, I used fix/momentum command to zero momentum in x,y direction.
#fix 4 upper setforce 0.0 0.0 NULL
fix 4 upper momentum 1 linear 1 1 0 angular
Unfortunately, it still moves in y direction.
Would anyone please help me to solve this problem?
Sincerely,
Joon
Your atoms probably have initial velocity in the y direction.
Zero it out via the velocity set command.
Steve
Dear Steve,
Thank you for your response.
However, it seems velocity set command does not work.
I zeroed the initial velocity in x,y direction by velocity set command as following,
velocity upper set 0.0 0.0 NULL units box
and,
fix 3 upper rigid single torque * off off off
fix 4 upper setforce 0.0 0.0 NULL
The model still translates in y-direction during simulation (approx. after 30 ps).
Is there any way to fix the model only to move in z-direction for entire simulation time?
Sincerely,
Joon
If you turn off forces in y (with an initial velocity of 0.0)
atoms will not move it that dir. If they are, then you haven't
done it right.
Steve