Platinum surface relaxation ( what is the suitable ISIF value?)

[neogien]

Hello!

I'm doing surface relaxation calculation of Platinum (111) surface.

I had completly calculated optimized lattice parameter, and made (111) layer slab.

I have no idea what value of ISIF should I use for my calculations.

Actually, I think, in real surface system the total volume of slab supercell should be fixed. So I allowed the relaxation of the cell shape and the lacation of ions in cell. (ISIF = 4)

Is this ISIF=4 reliable?

Or should I use the ISIF value 2(only the position of ions are allowed to relax) or 3(cell volume, shape and position of ions are all allowed to relax) for surface relaxation?

<span class='smallblacktext'>[ Edited ]</span>

[admin]

no, cell shape relaxations are appropriate for bulk cell optimations only as well. For slabs, only the ions' positions must be relaxed, hence use ISIF<3 ( or do not set it explicitely at all)