[Pw_forum] cell_dofree

[Francesco Macheda]

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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