Hi All,

I have a periodic cell (simulation box). I want to increase the cell size so that only the vaccum between the two surfaces increases from say 100 A to 120 A. I have attached a picture for a better explanantion of what i intend to do. (the figure may be a little misleading, I want to change the size of the cell in the z direction ONLY)

When I use "Lattice Parameters" option and change the length of c axis in 'Parameters' tab of this option, then the lattice size do increase but at the same time it stretches all other bonds. How can i increase the cell size without pulling the bonds or changing the atom positions?

Thanks.

nitin