velocity create command gives a strongly anisotropic velocity distribution

Dear all,

I'm facing a strange behavior of the velocity create command when
using the enclosed input script and data file.

With an old lammps version (12 Apr 2012), the created velocity
distribution is roughly isotropic as expected (temperatures measured
along x, y and z are roughly equals), but when using the latest svn
version (1 Jul 2012), the temperature is extremely small in one

I would be very happy if someone could help me solve this issue.

Best regards,

in.velocity (670 Bytes)

data.velocity (869 KB)

I've just run the scripts and the result is ok:

Step Temp Tx Ty Tz TotEng
       0 0.73 0.7378407 0.72115721 0.73133919 -2.205682

(LAMMPS 1 Jul 2012).

Rodrigo Freitas

There was a typo introduced in velocity.cpp
by a recent patch to allow image flags to be 64 bit.
Change this line:

      zbox = (image[i] >> IMG2BITS) - IMGMASK;
      zbox = (image[i] >> IMG2BITS) - IMGMAX;

in the zero_rotation() method.

Will post a patch this AM ...