Quick google search: http://quantum.phys.cmu.edu/groupth/gt21.pdf
On Fri, Jan 11, 2019 at 10:23 AM Offermans Willem <willem.offerm...@vito.be> wrote: > Sorry for my ignorance, but I still don’t see the point. > > Maybe a reference to some literature might help. > > > 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 > > > On 11 Jan 2019, at 09:58, Malte Sachs <malte.sa...@chemie.uni-marburg.de> > wrote: > > 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 > > <vito.jpg> > > On 10 Jan 2019, at 22:00, Paolo Giannozzi <p.gianno...@gmail.com> wrote: > > On Thu, Jan 10, 2019 at 4:30 PM Offermans Willem <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 ignored > their 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 list > users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users > > > Indien 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 > listusers@lists.quantum-espresso.orghttps://lists.quantum-espresso.org/mailman/listinfo/users > > > _______________________________________________ > users mailing list > users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users > > > _______________________________________________ > users mailing list > users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users -- 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
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