[Pw_forum] cell_dofree

[Paolo Giannozzi]

The only way to achieve what you like is to modify the code. See
"init_dofree" in Modules/cell_base.f90. Note that if you impose a
constraint, you have to ensure that it doesn't break some symmetry
that is present in the initial state

Paolo

On Mon, May 30, 2016 at 12:49 PM, Francesco Macheda
<macheda.franc at gmail.com> wrote:
> Hi everybody,
> I need a little help about cell_dofree type optimization. This is part of my
> input :
>
> ATOMIC_POSITIONS crystal
> Ge     0.00E+00  0.50E+00  0.75E+00    0 0 0
> Ge     0.50E+00  0.00E+00  0.25E+00    0 0 0
> Ge     0.00E+00  0.00E+00  0.00E+00    0 0 0
> Ge     0.50E+00  0.50E+00  0.50E+00    0 0 0
> CELL_PARAMETERS angstrom
> 2.825 2.825 0.0
> 2.6 2.6 0.0
> 0.0 0.0 5.65
>
> Now, i've seen all the cell_dofree options but I would like to make a
> vc-relax such that THE ENTIRE v_2 lattice vector is kept fixed whereas the
> other two vectors are free to move, and I've not found it possible by
> cell_dofree (only to fix the components can be choosen).
>
> I know that a possible solution is to rotate the crystal and then use
> cell_dofree on the cartesian components, but I would prefer to find a direct
> solution, if possible, because otherwise I would have to change a lot of
> other inputs.
> Thank you in advance,
> Francesco Macheda
> Graduating student at Pisa University
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222