[QE-users] TB09, TPSS

[Reinaldo Pis Diez]

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)
>>> users mailing list users at 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
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
> .