[lammps-users] triclinic (non-orthogonal) simulation box, fix_deform, displace_box

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1

Hi,

I have a problem using the fix_deform command for triclinic simulation boxes.
I'd like to use the fix to apply a shear deformation in order to investigate
plastic deformation of metals. I get errors in my results since when I
perform a xz-fix_deform, the atoms in z direction are remapped (as a result
of the periodic boundary conditions) in a way that avoids plastic deformation
(nucleation of dislocations, slip, ...).
So I'd like to use fixed boundary conditions in the z-direction, which is not
possible for a xz-fix_deform (at least at the moment...) or the
xz-displace_box command. Why must this direction be periodic? Is there a
possibility to apply shear using these commands without facing these
problems?

Thanks...

2

I'm not sure it makes sense to have a non-orthogonal simulation box
that isn't periodic in the dimensions that are non-orthogonal (x,z in
this case).
Have to think about it.

You can do what you are asking by using an orthogonal simulation box
and dragging the atoms at the z ends sideways to induce shear in the
reset of the sample. Like the image "Shear of Cu bicrystal" on the WWW
page under Pictures. Only there it is xy instead of xz.

Steve