[Pw_forum] Forces are not zero (for atoms in non-primitive cell)

[Duy Le]

Dear all,

I wonder if anyone knows how to vanish the forces acting on atoms in a
non-primitive cell. I saw that if I have 1x1x5 cell of Cu(111) (or any
other systems), the x-y components of forces are zero but when I make
2x2x5 or other supercell, these forces becomes non-zero. Of course,
these values are quite small. I used lot of significant digits for
coordinates and cell parameters but they do not help.

Many thanks.
----------------------------------------------------
Duy Le
Postdoctoral Associate
Department of Physics
University of Central Florida.
Website: http://www.physics.ucf.edu/~dle