[DFTB-Plus-User] Bandgap of GNR

u3129004 at edu.gifu-u.ac.jp u3129004 at edu.gifu-u.ac.jp
Sun Jan 17 06:16:31 CET 2016


Dear Gabriele,

I am sorry for my late reply. Thank you very much for your advice.

Sincerely yours,
Kazuma

----- Original Message -----
> On 01/13/2016 01:29 PM, u3129004 at edu.gifu-u.ac.jp wrote:
> > Dear Gabriele,
> > 
> > Thank you very much for your advice and teaching. 
> > Thank to you, using small boadening factor I could get the same 
result 
> > with yours. I would like to ask you additional questions:
> > 
> > *How should I decide whether structure is optimized or not? 
> > *And in order to optimize this geometry, how should I change the 
> > parameter?
> 
> Dear Kuzuma,
> 
> your input file contains the optimization section already (Driver =
> ConjugateGradient). See the manual, the Driver takes care of 
optimization.
> 
> Your system is not optimized if atomic forces are too large.
> 
> If you run an optimization the maximum force is given as output, and 
you
> can set a tolerance for the minimum force you what to achieve.
> 
> However, if you are not familiar with all these concepts, I suggest 
you
> to ask your supervisor a book on QM or DFT modelling. Many concepts 
will
> apply to DFTB too and it will be definitely more helpful than my
> explanations.
> 
> Best,
> Gabriele
> 
> > 
> > Sincerely yours,
> > Kazuma
> > 
> > ----- Original Message -----
> >> Dear Kazuma,
> >>
> >> the distance between layers in x direction is very large and there'
s 
> > no
> >> interaction between periodic images along x, therefore the band 
would 
> > be
> >> flat. You only need sampling beyond Gamma along direction with
> >> interaction between periodic images, y in your case.
> >>
> >> You structure is going to relax if allowed to, therefore the 
geometry 
> > is
> >> not optimized. In particular the C-H bond is shorter than the mio 
sk 
> > set
> >> would deliver.
> >>
> >> I used a small broadening factor in the DOS (0.01) to clearly
> >> distinguish the energy levels, or alternatively you can look for 
the
> >> highest occupied and lowest unoccupied level in the detailed.out. 
If I
> >> use the default broadening I get a very similar curve to yours, 
there'
> > s
> >> nothing wrong with it.
> >>
> >> You're probably trying to decide how large the gap is checking 
where 
> > the
> >> DOS goes to zero, but this is somewhat arbitrary because the DOS is 
> > also
> >> calculate given a finite broadening.
> >>
> >> If you try to calculate the band structure instead of the DOS you'
ll 
> > see
> >> the gap more clearly.
> >>
> >> Best,
> >> Gabriele
> >>
> >>
> >> On 01/13/2016 11:31 AM, u3129004 at edu.gifu-u.ac.jp wrote:
> >>> Dear Gabriele,
> >>>
> >>> Thank you very much for your early reply. I have questions.
> >>>
> >>> *Why I do not need k-points in x direction?
> >>> *I do not know the meaning you said "your structure seemed not 
> > optimized
> >>> ".
> >>>
> >>> In addition, I tried again,but the result is like an attached file.
 
> > what 
> >>> is the cause that my result do not agree with your result? I also 
> >>> attached the input file.
> >>>
> >>> Sincerely yours,
> >>> Kazuma 
> >>>
> >>> ----- Original Message -----
> >>>> Hi Kazuma,
> >>>>
> >>>> you don't need k-points in x direction here. I've run your input 
> > with
> >>>> the supercell folding set to 1 in x direction (left 25 in y). I 
> >>> lowered
> >>>> the force tolerance to 1e-3 too (didn't want to wait too long) 
and 
> > I 
> >>> get
> >>>> 1.42 eV (detail of dos around gap attached). Your structure 
seemed 
> > not
> >>>> optimized but this should not be the problem, even if I run the 
> > input 
> >>> as
> >>>> it is with the geometry you sent but removing optimization I get
> >>>> something around 1.3 eV. Maybe you do some mistake when 
evaluating 
> > the 
> >>> gap.
> >>>>
> >>>> Best
> >>>> Gabriele
> >>>>
> >>>>
> >>>> On 01/13/2016 10:04 AM, u3129004 at edu.gifu-u.ac.jp wrote:
> >>>>> Dear DFTB+ user,
> >>>>>
> >>>>> I calculated Density of states of graphene nanoribbon (please 
> > refer 
> >>> to 
> >>>>> an attached file). But I am doubtful of this result. Because the 
> >>> bandgap 
> >>>>> is a lot different from other calculation results which are 
> >>> calculated 
> >>>>> by Tight Binding method and first principal calculation. I 
> > attached 
> >>> my 
> >>>>> input file for this calculation.
> >>>>>
> >>>>> It would be very helpful if you could provide me any advice.
> >>>>>
> >>>>> Thank you in advance,
> >>>>> Kazuma
> >>>>> ---------------------------------------------------
> >>>>> Kazuma KIHIRA
> >>>>> Environmental & Renewable Energy Systems Division
> >>>>> Graduate School of Engineering, Gifu University
> >>>>> E-mail:u3129004 at edu.gifu-u.ac.jp
> >>>>> ---------------------------------------------------
> >>>>>
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> DFTB-Plus-User mailing list
> >>>>> DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >>>>> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

> > 
> >>>
> >>>>>
> >>>>
> >>>> -- 
> >>>> --
> >>>> Dr. Gabriele Penazzi
> >>>> BCCMS - University of Bremen
> >>>>
> >>>> http://www.bccms.uni-bremen.de/
> >>>> http://sites.google.com/site/gabrielepenazzi/
> >>>> phone: +49 (0) 421 218 62337
> >>>> mobile: +49 (0) 151 19650383
> >>>>  
> >>>> _______________________________________________
> >>>> DFTB-Plus-User mailing list
> >>>> DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >>>> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

> > 
> >>>
> >>>>
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> DFTB-Plus-User mailing list
> >>>> DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >>>> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

> > 
> >>
> >> -- 
> >> --
> >> Dr. Gabriele Penazzi
> >> BCCMS - University of Bremen
> >>
> >> http://www.bccms.uni-bremen.de/
> >> http://sites.google.com/site/gabrielepenazzi/
> >> phone: +49 (0) 421 218 62337
> >> mobile: +49 (0) 151 19650383
> >> _______________________________________________
> >> DFTB-Plus-User mailing list
> >> DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

> > 
> >>
> > 
> > 
> > _______________________________________________
> > DFTB-Plus-User mailing list
> > DFTB-Plus-User at mailman.zfn.uni-bremen.de
> > https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

> > 
> 
> -- 
> --
> Dr. Gabriele Penazzi
> BCCMS - University of Bremen
> 
> http://www.bccms.uni-bremen.de/
> http://sites.google.com/site/gabrielepenazzi/
> phone: +49 (0) 421 218 62337
> mobile: +49 (0) 151 19650383
> _______________________________________________
> DFTB-Plus-User mailing list
> DFTB-Plus-User at mailman.zfn.uni-bremen.de
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> 




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