Karim,
I'd say that the basis set deosn't play as much an influence on the final
symmetry of the unit cell (at least in Siesta) as much as a fine real-space
mesh. However, if you know which symmetrization operations on forces and
stresses maintain the symmetry of a cell, then you can implement them in the
file constraints.f, re-compile siesta and use
%block GeometryConstraints
routine constr
%endblock GeometryConstraints
in your fdf file.Of course, you are advised to check the manual for the
exact syntax of this block, as well as the programming of the constraints in
this file :)
Marcos
On Sun, Jan 30, 2011 at 12:03 PM, karim rezouali <[email protected]>wrote:
> Dear Users,
>
> Is there a way to relaxe both atomic positions and cell vectors ( variable
> cell optimization) of a given system without changing the shape of the
> supercell (preserving the symmetry) by a judicious choice of PAO basis
> sets?
>
>
> Karim
>
>
