question regarding kspace

Hi all:

I have a question regarding kspace modify in lammps, specifically about “ kspace modify slab” option. Considering the following 2 simulations with the same atomic configurations. The first one uses non-periodic boundary condition in z and kspace modify slab 3.0. The second one uses PBC in all directions but has a vacuum space above the sample in z direction so that lz_new = lz_old*v_factor. To let the two simulations yield the same energy, v_factor should be 3 or 4 ? Our result indicate that v_factor = 4. But looking at the source code we guess v_factor should be 3.

Thanks

Deena

PS. Sending the mail one more time

Hi all:

I have a question regarding kspace modify in lammps, specifically about “
kspace modify slab” option. Considering the following 2 simulations with
the same atomic configurations. The first one uses non-periodic boundary
condition in z and kspace modify slab 3.0. The second one uses PBC in all
directions but has a vacuum space above the sample in z direction so that
lz_new = lz_old*v_factor. To let the two simulations yield the same energy,
v_factor should be 3 or 4 ? Our result indicate that v_factor = 4. But
looking at the source code we guess v_factor should be 3.

Thanks

Deena

PS. Sending the mail one more time

why? the question has already been answered.