Is there any way I stretch the two cubes in different extent of elongation?

Hello, all

I want to simulate a problem about interface between two cubes.
A force perpendicular to the interface is exerted in order to
keep the two cubes contact with each other. These two cubes are
filled with perfect lattices and have periodic boundary
at the direction parallel to the interface.

Now I want to stretch the two cubes at one direction parallel
to the interface, especially I hope the two cubes have different
extent of elongation at that direction.

It seems the fix deform will change the dimension of the whole box.
But in this problem, I hope the extent of elongation is different
between the cube above the interface and the cube below the interface.

Is there any way to achieve it? If possible, how can I exert it?

Thank you in advance!

Wang Kai

If I understand your description, you have a periodic
dimension and 2 lattices (in the 2 cubes) in that
direction, with different lattice constants. You can
use fix deform (in that dimension) to stretch the
box and the 2 lattices, by the same amount. If you want
them stretched different amounts, then I don't see how
that is possible, since they are both periodic.