COM motion

Francesco francesc... at
Thu May 22 09:04:16 UTC 2008


I am running cp2k on an isolated molecule (poisson_solver wavelet,
etc). I started with the
molecule centered in the box, but I've seen that it moves around the
box. After 10000
steps it even arrives close to the borders, and cp2k complains that
the density hits the
boundaries.  In the output I've seen that the COM has small
velocities, so I think I have
to freeze movements and rotations of the whole system.

In the cp2k input manual I've found the COMVEL_TOL keyword.

If I leave the default value COMVEL_TOL 0.0, the COM seems to move. A
typical step shows:
Centre of mass motion (COM):
x =      -0.0000002303
y =       0.0000002945
z =      -0.0000001305

if I put COMVEL_TOL 1e-8, in the log file I have:

Temperature scaled to requested temperature:     85.43 K  ->     85.43
MD| Old VCOM =    -0.0000002303    0.0000002945   -0.0000001305 a.u.
MD| New VCOM =    0.0000000000    0.0000000000    0.0000000000 a.u

1) Is this the correct way to block the motion of COM ?
2) What about rotations ? Is ANGVEL_ZERO T ok ?


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