[Pw_forum] problem in determine cell_factor

[Lorenzo Paulatto]

On 01/15/2014 05:27 PM, ehsan targholi wrote:
> how i can determine the best value of cell_factor parameter for my cell?

Just put it large enough, i.e. 3. But be aware that if the volume
changes so much, the initial guess may have been quite bad,.

> my cell is graphene sheet with 55  atom of carbon


Are you sure that doing a variable cell relax calculation of a 2D
supercell is a good idea? You should at the very least block the
relaxing of the out-of-plane axis.

best regards

-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone:+33 (0)1 44275 084 / skype: paulatz
www:  http://www-int.impmc.upmc.fr/~paulatto/
mail: 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 5