Hello,
I cannot reproduce this with current development version. Any attempt
of using a PBE density as the starting point for a TB09 calculation
ends up with:
Error in routine read_rhog (1):
error reading file ./s.save/ekin-density
This happens if I run scf with PBE and then nscf with TB09, or scf
with PBE followed by scf with TB09 (restart_mode='restart').
Any suggestion would be appreciated.
Thanks,
Michal Krompiec
Merck KGaA
On Wed, 6 Nov 2019 at 19:36, Fabio Costa <fabiocos...@hotmail.com> wrote:
>
> Dear users and developers
>
> After some more attempts to use the TB09 functional, I ended up finding this
> previous post:
> https://lists.quantum-espresso.org/pipermail/users/2019-April/042619.html ,
> and after changing v_of_rho.f90, the code is now able to end without any
> error.
>
> In my attempts, I'm performing the calculations as an initial scf run with a
> PBE pseudopotencial, and then another scf run, now with restart_mode =
> 'restart' and input_dft = 'MGGA_X_TB09'. By following this procedure, as
> described in E. Germaneau's paper, the calculations do converge.
>
> The issue now is that the gap energies I'm finding are very large. For
> example, for silicon, the calculations result in a 2.8 eV gap, larger even
> than the results presented in the paper, where the values ranged between 1.9
> to 2.3. Despite the large gaps, the band structure and DOS agree well with
> the ones obtained with PBE.
>
> Is there any way to improve these results. My first guess is to adjust the
> "c" parameter in the mBJ functional. After some searching through the
> routines and Libxc files, I'm still clueless on how to proceed on this matter.
>
> Any further suggestions will be much appreciated
>
> Thank you
> Fábio Costa
>
>
>
> ________________________________
> De: users <users-boun...@lists.quantum-espresso.org> em nome de Fabio Costa
> <fabiocos...@hotmail.com>
> Enviado: segunda-feira, 14 de outubro de 2019 13:10
> Para: users@lists.quantum-espresso.org <users@lists.quantum-espresso.org>
> Assunto: [QE-users] On the use of the modified Becke-Johnson (TB09) functional
>
> Dear all
>
> I'm having some difficulties to work with the TB09 functional. After some
> reading, I found in some old posts that this can be done by compiling QE
> with Libxc, and by adding the line 'input_dft='tb09'' in the pw.x input.
>
> When I try to use this functional, the scf calculation always ends like this:
>
> total energy = NaN Ry Harris-Foulkes
> estimate = -11.24358313 Ry estimated scf accuracy <
> 0.01858366 Ry iteration # 18 ecut= 120.00 Ry beta= 0.10
> Davidson diagonalization with overlap
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> Error in routine cdiaghg (7): eigenvectors failed to converge
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> What draws my attention is that always in the last cycle before the error the
> total energy is printed as NaN. The parameters to the calculation seem to be
> fine, as it ends smoothly without the input_dft line.
>
> By searching in the QE user guide, there is a reference to the work of E.
> Germaneau, which lead me to his paper (DOI: 10.1016/j.cpc.2013.02.020), where
> the results of his implementation are presented. Even though, it is unclear
> to me how to use the functional correctly.
>
> Thanks for any assistance
> Fábio Costa
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