[Pw_forum] problem with symmetry recognition

[Vic Bermudez]

Hi Pascal,

	If I understand correctly, you're trying to optimize the unit cell while
constraining 2 of the lattice constants to remain equal, as required by
symmetry. I don't think that QE allows this. If you do a "vc-relax", what
seems to happen is that symmetry is ignored, and all lattice constants are
varied independently. I've attached a script written by a colleague that
does repeated single-point runs for a range of lattice constants. You can
then fit points near the total-energy minimum to find the exact minimum. Of
course, this has to be done iteratively if more than one lattice constant is
being optimized.
	Hope this helps.

	Best Wishes,
	Vic Bermudez

Victor M. Bermudez
Code 6876
U.S. Naval Research Laboratory
4555 Overlook Ave., S.W.
Washington, DC 20375-5347

-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: QE_loop.csh.txt
Url: http://www.democritos.it/pipermail/pw_forum/attachments/20110709/40d75653/attachment.txt