Your question is based upon a common misunderstanding of minimizing forces. You are thinking that the time to optimize depends upon the number of positions (3*Number of Pt atoms that move) which is wrong. With PORT it scales as the number of clusters of phonon frequencies and weakly with the width of the clusters; with MSR1a it scales as the number of clusters of eigenvalues of the joint electron-phonon problem and their width.You will gain far more by generating a proper symmetric model with P-3m1 (maybe P-31m) symmetry rather than what you appear to have, a P1 structure. This will reduce the number of uniques phonon etc modes by something like 6-12, and will be much faster and converge better.

Dear Laurence Marks,

`When having created the most symmetric slab model that is relevant for`

`the case at hand, wouldn't you agree that it still makes sense to fix`

`the positions of the middle few layers to their bulk positions? One`

`cannot make slabs as thick as to find spontaneously bulk behaviour in`

`the center, and therefore imposing the bulk geometry in the slab center`

`could be preferred over getting unphysical lattice spacings. Can you`

`comment?`

Thanks, Stefaan -- Stefaan Cottenier Center for Molecular Modeling (CMM) & Department of Materials Science and Engineering (DMSE) Ghent University Tech Lane Ghent Science Park – Campus A building 903 BE-9052 Zwijnaarde Belgium http://molmod.ugent.be http://www.ugent.be/ea/dmse/en email: stefaan.cotten...@ugent.be my conference talks on Youtube: http://goo.gl/P2b1Hs for China: http://i.youku.com/cottenierlectures _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html