[QE-users] TB09, TPSS

[Michal Krompiec]

Dear Reinaldo,
Thanks, this sounds very promising! Did you have to use a tighter FFT
grid or did the default work fine?
Best,
Michal Krompiec
Merck KGaA

On Thu, 21 May 2020 at 13:20, Reinaldo Pis Diez
<reinaldo.pisdiez at gmail.com> wrote:
>
> Dear Michal and folks,
>
> A few days ago I've faced exactly the same problem after recompiling
> QE 6.5 with LibXC 4.3.4 to use TB09 to see its effect on the band
> gap of some semiconductors.
>
> What I saw instead is that an scf run of the SCAN functional, also a
> metaGGA one, converges smoothly on top of a scf, relax or vc-relax
> job using PBE, for example. TB09 and the others metaGGA available
> show the divergent behavior you are mentioning.
>
> Then, I tried a TB09 job on top of the converged SCAN calculation
> using restart_mode = 'restart' and the job converged in a few
> iterations, no divergence was observed. After the TB09 scf job
> converged, I was able to run nscf and bands jobs to obtain both DOS
> and band structures.
>
> I understand this is not a solution, but a workaround as a more
> elegant solution is found.
>
> Regards,
>
> Reinaldo Pis Diez
> Center of Inorganic Chemistry
> National University of La Plata
> Argentina
>
> > Dear Paolo,
> > I changed io_rho_xml.f90 so that if the kinetic energy density file
> > isn't found, the array is set to 0:
> >
> > 155d144
> > <       LOGICAL :: ekin_density_exists
> > 172,180c161,164
> > <          INQUIRE( FILE=TRIM(dirname) // "ekin-density",
> > EXIST=ekin_density_exists)
> > <          IF ( ekin_density_exists ) THEN
> > <            CALL read_rhog( TRIM(dirname) // "ekin-density", &
> > <              root_bgrp, intra_bgrp_comm, &
> > <              ig_l2g, nspin_, rho%kin_g, gamma_only )
> > <            WRITE(stdout,'(5x,"Reading meta-gga kinetic term")')
> > <          ELSE
> > <            rho%kin_g = 1.0
> > <          ENDIF
> >
> > Now I can start a TB09 calculation from a PBE density, but still my
> > test case diverges immediately (=faster than when starting from
> > scratch), regardless of diagonalization method. For example:
> >       The initial density is read from file :
> >       ./sic.save/charge-density
> >
> >       Starting wfcs from file
> >
> >       total cpu time spent up to now is        0.3 secs
> >
> >       Self-consistent Calculation
> >
> >       iteration #  1     ecut=    82.00 Ry     beta= 0.40
> >       CG style diagonalization
> >
> >
> >   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >       Error in routine c_bands (1):
> >       too many bands are not converged
> >   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >
> > I would be very grateful for any suggestions.
> > Best,
> > Michal
> >
> > P.S. This is my input file:
> > &CONTROL
> >      calculation  = "scf"
> >      prefix       = "sic"
> > /
> >
> > &SYSTEM
> >      a           =  4.34800e+00
> >      ibrav       = 1
> >     ecutwfc          = 82
> >     ecutrho          = 328
> >      nat         = 8
> >      ntyp        = 2
> >      occupations = "fixed"
> > input_dft='tb09'
> > /
> > &ELECTRONS
> >     electron_maxstep = 1000
> >     conv_thr         = 1e-10
> >     mixing_mode      = 'plain'
> >     mixing_beta      = 0.4
> >    startingpot = 'file'
> >    startingwfc = 'file'
> >    diagonalization = 'cg'
> > /
> >
> > K_POINTS automatic
> > 8 8 8   1 1 1
> >
> > ATOMIC_SPECIES
> > Si     28.08500  Si.upf
> > C      12.01060  C.upf
> >
> >
> > ATOMIC_POSITIONS {angstrom}
> > Si      0.000000   0.000000   0.000000
> > Si      0.000000   2.174000   2.174000
> > Si      2.174000   0.000000   2.174000
> > Si      2.174000   2.174000   0.000000
> > C       1.087000   1.087000   1.087000
> > C       1.087000   3.261000   3.261000
> > C       3.261000   1.087000   3.261000
> > C       3.261000   3.261000   1.087000
> >
> > On Fri, 8 May 2020 at 09:39, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:
> >> On Thu, May 7, 2020 at 10:33 PM Michal Krompiec <michal.krompiec at gmail.com> wrote:
> >>
> >>>   it was suggested to start from a density calculated with a different functional, but when I try to read in PBE density, it complains that it cannot read the kinetic energy file (which obviously cannot be there).
> >>
> >> this can be easily changed, I think: just disable the check and set the kinetic energy density to zero
> >>
> >>> Should TPSS or SCAN pseudos work better (and where do I get them from)?
> >>
> >> I don't think the problem is in the pseudos but in the nasty numerical behavior of meta-GGAs. See for instance here: https://gitlab.com/QEF/q-e/-/issues/32. Note that several bugs have been fixed in the development version.
> >>
> >> Paolo
> >>
> >>> Thanks,
> >>> Michal Krompiec
> >>> Merck KGaA
> >>>
> >>> _______________________________________________
> >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
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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
> >>
> >> _______________________________________________
> >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
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> > .
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