Dear Özcan,

Indeed you can model a molecule using ibrav = 1. In this case, you should ensure that the cell parameter is sufficiently large to avoid interactions among the periodic images. In other words, one describes the molecule within a simple cubic Bravais lattice while keeping it isolated, as a molecule should be. If we use ibrav equals 0 (free lattice), and write only the value of one lattice parameter, we are imposing a simple cubic symmetry by hand. In addition, you can include the flag 'assume_isolated' to improve the description of a molecular system.

Regards,

Enesio Marinho Jr.

Enesio Marinho Jr many thanks for your reply. Yes, we should guarantee to isaloted the molecule from any interaction as you suggested. I will determine ibrav=1 and apply vacuum with highest level.

Many thanks Enesio,

Best,

Merve