lammps-users Digest, Vol 69, Issue 9

Dear Ravi and Steve,

I am highlighting the fix deform command used by Ravi:

fix 1 all deform 1 x volume y volume z scale 10.1 units box

Will the use of volume option in this command give the correct results? I am saying this since the Poisson’s ratio of Zirconium is 0.34 and in the manual it is written that "Using the volume style for those 2 dimensions to keep the box volume constant may make more physical sense, but may also not be correct for materials and potentials whose Poisson ratio is not 0.5. "

As I see Ravi’s input script, I do not see any other fix command (NVE or NVT) to integrate the equation of motions. Fix deform does not include the integration of equation of motions.

I would like to appreciate Steve’s comments and comments from LAMMPS users on the use of volume option in fix deform command for Zirconium or any other material whose Poisson’s ratio is not 0.5.

With best regards,

The comment about the Poisson's ratio = 0.5
on the fix deform doc page is not really about
LAMMPS. It's about whether you should use
a volume-preserving deformation or not for
various materials and potentials. That's up to
you to decide.