[ase-users] Non-zero center of mass velocity in MD simulation

[Zeeshan Ahmad]

Hi ase-users and developers,

During my NVT MD simulation, the center of mass acquires a non-zero velocity and moves out of the computational box after ~5000 time steps. I am using a reasonable time step of 2 fs. 

dynDiff = NPT(atoms=atoms,timestep=timestep*units.fs,temperature=Treq*units.kB, pfactor = None, mask = (0,0,0),ttime = ttime*units.fs,externalstress=0,logfile='Diff.log',loginterval=1)

I was wondering about the best way to keep the center of mass velocity zero. One solution would be to use the Stationary function in the ase.md.velocitydistribution module and attach it as an observer function to the dynamics object, so that it sets the velocity to zero at every iteration (Seems very artificial though).

from ase.md.velocitydistribution import Stationary
dynDiff.attach(Stationary(atoms = atoms))

Do you have any suggestions?

Thank you
--
Zeeshan Ahmad
PhD student, Mechanical Engineering
Carnegie Mellon University
email: azeeshan at andrew.cmu.edu <mailto:azeeshan at andrew.cmu.edu>
http://www.andrew.cmu.edu/user/azeeshan/ <http://www.andrew.cmu.edu/user/azeeshan/>






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