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!