Dear Willem,in case of a screw axis or a glide plane you couple a rotation or a mirrow with a fractional translation (e.g. 1/2 or 1/3 of a lattice vector).
Best, Malte Am 11.01.2019 um 09:03 schrieb Offermans Willem:
Dear Paolo and Quantum Espresso friends, I’m sorry, but your explanation did not enlighten me.Your response: "it means that the symmetry operation consists in a rotation (or a rotation + spatial inversion) plus a translation (not a lattice one)” don’t ring a bell.What kind of translational symmetry are you talking about, if not the lattice one?My system has S2-Symmetry. This means a rotation about 180°, followed by reflection in a plane perpendicular to the rotation axis. It can be shortened to an inversion centre. Combined with the identity operation, this leads to 2 Sym.Ops, which have been detected by the program. This is consistent with the message in the output. Since I’m dealing with a slab, the system also has translational symmetry. I don’t see why the inversion centre should be incommensurate with this translational symmetry.What is the connection to the FFT grid? Met vriendelijke groeten, Mit freundlichen Grüßen, With kind regards, Willem Offermans Researcher Electrocatalysis SCT VITO NV | Boeretang 200 | 2400 Mol Phone:+32(0)14335263 Mobile:+32(0)492182073 willem.offerm...@vito.be <mailto:willem.offerm...@vito.be>On 10 Jan 2019, at 22:00, Paolo Giannozzi <p.gianno...@gmail.com <mailto:p.gianno...@gmail.com>> wrote:On Thu, Jan 10, 2019 at 4:30 PM Offermans Willem <willem.offerm...@vito.be <mailto:willem.offerm...@vito.be>> wrote:2 Sym. Ops., with inversion, found ( 1 have fractional translation) [...] What does it mean?it means that the symmetry operation consists in a rotation (or a rotation + spatial inversion) plus a translation (not a lattice one)At some point in the sequence of calculations, the output contained the following message about symmetry: No symmetry found I was surprised about the lost of symmetry. Is it related to the fractional translation?no, unless this happens in the last scf step, in which the FFT grid may change, in which case this is what may happen:(note: 1 additional sym.ops. were found but ignoredtheir fractional translations are incommensurate with FFT grid)Paolo -- Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 <vito.jpg>_______________________________________________ users mailing listusers@lists.quantum-espresso.org <mailto:users@lists.quantum-espresso.org>https://lists.quantum-espresso.org/mailman/listinfo/usersIndien u VITO Mol bezoekt, hou aub er dan rekening mee dat de hoofdingang voortaan enkel bereikbaar is vanuit de richting Dessel-Retie, niet vanuit richting Mol, zie vito.be/route. <http://www.vito.be/route> If you plan to visit VITO at Mol, then please note that the main entrance can only be reached coming from Dessel-Retie and no longer coming from Mol, see vito.be/en/contact/locations. <http://www.vito.be/en/contact/locations>VITO Disclaimer: http://www.vito.be/e-maildisclaimer _______________________________________________ users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
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