[QE-users] symmetry error in phonon output file

[Stefano Baroni]

Also said “small group” of the q vector. Please take the time to spend a couple of hours in the nearest library and look for some texts in group theory or “traditional” electronic-structure theory (Bassani and Pastori Parravicini would do). Make sure you understand what you read. If you don’t, try harder. Then revert to us, if need be. SB

--
Stefano Baroni, Trieste -- swift message written and sent on the go

> On 11 Sep 2018, at 12:26, Anindya Bose <anindya at iiita.ac.in> wrote:
> 
> Dear Sir,
> You are absolutely correct,I am getting exactly these symmetries.But transformation into D2h symmetries making the result incorrect and unphysical.Please tell me how to resolve this.
> Thanks and regards,
> Anindya Bose
> 
> On Tuesday, September 11, 2018, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:
> > These symmetries?
> >      Calculation of q =    0.0000000   0.0000000   0.0000000
> >      Mode symmetry, D_6h(6/mmm) point group
> >      Calculation of q =    0.0000000   0.1443376   0.0000000
> >      Mode symmetry, C_2v (mm2)  point group
> >      Calculation of q =    0.0000000   0.2886751   0.0000000
> >      Mode symmetry, C_2v (mm2)  point group
> >      Calculation of q =    0.0000000   0.4330127   0.0000000
> >      Mode symmetry, C_2v (mm2)  point group
> >      Calculation of q =    0.0000000  -0.5773503   0.0000000
> >      Mode symmetry, D_2h (mmm)  point group
> >      Calculation of q =    0.1250000   0.2165064   0.0000000
> >      Mode symmetry, C_2v (mm2)  point group
> > "Mode symmetry" means symmetry subgroup that leaves that wave-vector q unchanged.
> >
> >
> > On Tue, Sep 11, 2018 at 9:02 AM, Anindya Bose <anindya at iiita.ac.in> wrote:
> >>
> >> Dear Experts,
> >> While doing the phonon calculation of Graphene,I am getting a symmetry error in my ph.out files.Initially the file ph.out showing the correct symmetry of the material(e.g. Graphene D_6h point group symmetry) but after some interval it is showing some erroneous point  group symmetry D_2h.I am very much confused with this absurd result.What should I do here?I have played with conv_threshold (tried to reduce)but I was unsuccessful.How can I resolve this problem? A copy of ph.out file is enclosed with this mail. I will be waiting for a positive suggestion.
> >> Thanks and regards,
> >> Anindya Bose
> >> Research Fellow,
> >> Indian Institute of Information Technology,Allahabad
> >>
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> >
> >
> >
> > --
> > 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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