[QE-users] Problem in ph.x and epw.x (Wrong classes for C_3v) -

[Paolo Giannozzi]

As explained more than once: if you heavily rely upon symmetry, you should
provide your structure using the bravais lattice index and symmetric
positions with many significant digits, or better, with Wyckoff positions

Paolo

On Mon, Jun 10, 2019 at 5:33 PM Gopalan, Sanjay <Sanjay.Gopalan at utdallas.edu>
wrote:

> Dear all,
>
>
> I have been trying to calculate el-ph coupling constant for monolayer
> MoTe2 using QE and EPW.
>
>
> While calculating the phonon energies using ph.x I get error as
>
>
>      task #         3
>      from divide_class : error #         1
>      Wrong classes for C_3v
>
> But when I add the tag search_sym=.FALSE. as directed in this
> https://lists.quantum-espresso.org/pipermail/users/2017-August/039055.html,
> I am able to calculate the phonon energies.
>
> But, when I try to calculate el-ph coupling constant using EPW, I get the
> same error. Is there any way to switch off symmetry in EPW or other ways to
> overcome this error in ph.x?
>
> My scf input file
>
> &CONTROL
>   calculation='scf',
>   outdir='./',
>   prefix='calc',
>   pseudo_dir='./',
>   verbosity='low',
>   wf_collect= .true.
> /
>
> &SYSTEM
>
>     ibrav=0,
>     nat= 3, ntyp= 2, nbnd= 27,
>     ecutwfc = 60, ecutrho=240,
>     occupations = 'fixed'
>
> /
>
> &ELECTRONS
>   conv_thr=1d-9,
>   mixing_beta=0.7d0,
> /
> ATOMIC_SPECIES
>
>   Mo 95.96 Mo_ONCV_PBE_sr.upf
>   Te 127.6 Te_ONCV_PBE_sr.upf
>
> ATOMIC_POSITIONS (crystal)
> Mo       0.333333015000d0   0.333333015000d0   0.154510160000d0
> Te       0.666666985000d0   0.666666985000d0   0.226882756000d0
> Te       0.666666985000d0   0.666666985000d0   0.082149790000d0
>
> K_POINTS {automatic}
>   12 12 1 0 0 0
>
> CELL_PARAMETERS (angstrom)
>    1.779701562000d0   3.082533129000d0   0.000000000000d0
>   -1.779701562000d0   3.082533129000d0   0.000000000000d0
>    0.000000000000d0   0.000000000000d0  25.000000000000d0
>
> and ph.x input file
>
> MoTe2_phonon
>  &inputph
>   recover=.true.,
>   tr2_ph=1.0d-16,
>   prefix='calc',
>   fildvscf='dvscf',
>   amass(1)=95.960d0
>   amass(2)=127.60d0
>   outdir='./',
>   ldisp=.true.,
>   nq1=6,nq2=6,nq3=1,
>   fildyn='calc.dyn',
>  search_sym=.FALSE.
>  /
>
> Thank you
> Sanjay Gopalan
> Research Assistant
> University of Texas at Dallas
>
>
>
> _______________________________________________
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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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