On Thu, 2015-11-26 at 07:24 +0100, Matej Huš wrote: > Found the culprit! > When I turned off the dipole correction, the system converged.
Your vacuum thickness was indeed much too thin for the dipole correction. I am surprised that you even achieved the SCF convergence. Roughly, the vacuum thickness should be cca. doubled when using dipole correction, because you need a thick enough vacuum layer from the top of the slab to the dipole layer and from the dipole layer to the bottom of the adjacent slab. As a bare minimum: at least 6 Angstroms + dipole-layer (eopreg) + 6 Angstroms. But it would be better and safer to use even larger vacuum thickness, say, 8A + eopreg + 8A. It is a very good exercise to monitor, at least, the SCF energy as a function of vacuum thickness with the dipole correction to get the feeling of how much vacuum is needed in this case. Here take caution about the molecule: a taller (bigger) molecule will require larger separation between adjacent slabs than a short (small) molecule (by slab I mean just a metal-slab w/o molecule). You should also have some safe margin, e.g., if molecule rotates from parallel to perpendicular orientation ... Best regards, Tone PS: one more remark: you have used the opposite slab orientation as conventionally used, i.e., typically the molecule is put on top of the slab. Of course, the results do not depend on this choice, but you may face some problems to describe the results, because the jargon used in the surface science assumes the molecule above the surface (i.e. on top of the slab). For example, "atom moves up" would mean away from the surface ... -- Anton Kokalj J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia (tel: +386-1-477-3523 // fax:+386-1-477-3822) Please, if possible, avoid sending me Word or PowerPoint attachments. See: http://www.gnu.org/philosophy/no-word-attachments.html _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
