[DFTB-Plus-User] Band Gap calculation

Tue Nov 20 19:12:54 CET 2018

Dear Ben,
I really appreciate your response.
Please check the required files.
FYI, I used the SK files of the following types: 3ob, pbc, matsci,
mio, and all of them gave wrong band gap.

Regards

On Sun, Nov 18, 2018 at 11:04 PM Ben Hourahine <
benjamin.hourahine at strath.ac.uk> wrote:

> The mio set with default code option (non-SCC) is probably a reasonable
> choice.
>
> If you send me your full input (GGA geometry as well as the dftb_in.hsd)
> off list, I can investigate further.
>
> Regards
>
> Ben
>
> On 18/11/18 08:09, Sarah Gamal wrote:
>
> Any help please?
>
> On Mon, Nov 12, 2018 at 4:02 PM Sarah Gamal <s.abouelhasab at gmail.com>
> wrote:
>
>> I don't think using extra K points can not be the reason,
>> Which type of Slater Koster files should I use?
>> If I used the wrong files, may this cause this large difference in the
>> band gap?
>> I used the files for solids and surfaces.
>>
>> On Wed, Nov 7, 2018 at 7:16 PM Ben Hourahine <
>> benjamin.hourahine at strath.ac.uk> wrote:
>>
>>> Hello Sarah,
>>>
>>> might the the extra points in DFTB be at locations in the Brilouin zone
>>> where the gap is smaller and which are not sampled for siesta/espresso?
>>>
>>> Regards
>>>
>>> Ben
>>> On 05/11/2018 11:28, Sarah Gamal wrote:
>>>
>>> 1)Are you comparing equivalent k-points between the different codes?
>>>
>>>
>>> *Yes and I used more KPOINTS in DFTB*
>>>
>>> 2) What DFT functional are you using? DFTB functional tends to be
>>> similar to GGA but with an overestimation of the gap in most cases (LDA
>>> might be giving a smaller value).
>>>
>>> *We have used GGA in DFT *
>>>
>>>
>>> 3) Is there anything special about the electronic structure of this
>>> system (flat band correlation effects in moiré graphene)?
>>>
>>>
>>> *Not pure flat, see attached file (black for spin up and blue for spin
>>> down) *
>>> Regards
>>>
>>> On Mon, Nov 5, 2018 at 1:19 PM Sarah Gamal <s.abouelhasab at gmail.com>
>>> wrote:
>>>
>>>> 1)Are you comparing equivalent k-points between the different codes?
>>>>
>>>>
>>>> *Yes and I used more KPOINTS in DFTB*
>>>>
>>>> 2) What DFT functional are you using? DFTB functional tends to be
>>>> similar to GGA but with an overestimation of the gap in most cases (LDA
>>>> might be giving a smaller value).
>>>>
>>>> *We have used GGA in DFT *
>>>>
>>>>
>>>> 3) Is there anything special about the electronic structure of this
>>>> system (flat band correlation effects in moiré graphene)?
>>>>
>>>>
>>>> *Not pure flat, see attached file (black for spin up and blue for spin
>>>> down) *
>>>> Regards
>>>>
>>>> On Mon, Nov 5, 2018 at 8:01 AM Sarah Gamal <s.abouelhasab at gmail.com>
>>>> wrote:
>>>>
>>>>> 1)Are you comparing equivalent k-points between the different codes?
>>>>>
>>>>>
>>>>> *Yes and I used more KPOINTS in DFTB*
>>>>>
>>>>> 2) What DFT functional are you using? DFTB functional tends to be
>>>>> similar to GGA but with an overestimation of the gap in most cases (LDA
>>>>> might be giving a smaller value).
>>>>>
>>>>> *We have used GGA in DFT *
>>>>>
>>>>>
>>>>> 3) Is there anything special about the electronic structure of this
>>>>> system (flat band correlation effects in moiré graphene)?
>>>>>
>>>>>
>>>>> *Not pure flat, see attached file (black for spin up and blue for spin
>>>>> down) *
>>>>> Regards
>>>>>
>>>>> [image: image1.tiff]
>>>>>
>>>>> On Nov 4, 2018, at 3:29 PM, Ben Hourahine <
>>>>> benjamin.hourahine at strath.ac.uk> wrote:
>>>>>
>>>>> Hello Sarah,
>>>>>
>>>>> Thoughts so far:
>>>>>
>>>>> 1) Are you comparing equivalent k-points between the different codes?
>>>>>
>>>>> 2) What DFT functional are you using? DFTB functional tends to be
>>>>> similar to GGA but with an overestimation of the gap in most cases (LDA
>>>>> might be giving a smaller value).
>>>>>
>>>>> 3) Is there anything special about the electronic structure of this
>>>>> system (flat band correlation effects in moiré graphene)?
>>>>> Regards
>>>>>
>>>>> Ben
>>>>>
>>>>> On 04/11/18 10:58, Sarah Gamal wrote:
>>>>>
>>>>> This is the right file.
>>>>> Sorry for the disturbance.
>>>>>
>>>>> On Sun, Nov 4, 2018 at 12:56 PM Sarah Gamal <s.abouelhasab at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Dear,
>>>>>> I am working on a project and we need to calculate the band gap for
>>>>>> graphene nanomesh.
>>>>>> The band gap was calculated for the same system by siesta and
>>>>>> espresso and it was 0.7 eV.
>>>>>> When it's calculated by DFTB+ it was about 0.185 eV.
>>>>>>
>>>>>> What do you think the problem?
>>>>>> I attached the input file, should I add any parameters?
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> DFTB-Plus-User mailing listDFTB-Plus-User at mailman.zfn.uni-bremen.dehttps://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
>>>>>
>>>>>
>>>>> --
>>>>>       Dr. B. Hourahine, SUPA, Department of Physics,
>>>>>     University of Strathclyde, John Anderson Building,
>>>>>             107 Rottenrow, Glasgow G4 0NG, UK.
>>>>>     +44 141 548 2325, benjamin.hourahine at strath.ac.uk
>>>>>
>>>>> 2013/4 THE Awards Entrepreneurial University of the Year
>>>>>       2012/13 THE Awards UK University of the Year
>>>>>
>>>>>    The University of Strathclyde is a charitable body,
>>>>>         registered in Scotland, number SC015263
>>>>>
>>>>> _______________________________________________
>>>>> 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 listDFTB-Plus-User at mailman.zfn.uni-bremen.dehttps://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
>>>
>>> --
>>>       Dr. B. Hourahine, SUPA, Department of Physics,
>>>     University of Strathclyde, John Anderson Building,
>>>             107 Rottenrow, Glasgow G4 0NG, UK.
>>>     +44 141 548 2325, benjamin.hourahine at strath.ac.uk
>>>
>>> 2013/4 THE Awards Entrepreneurial University of the Year
>>>       2012/13 THE Awards UK University of the Year
>>>
>>>    The University of Strathclyde is a charitable body,
>>>         registered in Scotland, number SC015263
>>>
>>> _______________________________________________
>>> 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 listDFTB-Plus-User at mailman.zfn.uni-bremen.dehttps://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
>
>
> --
>       Dr. B. Hourahine, SUPA, Department of Physics,
>     University of Strathclyde, John Anderson Building,
>             107 Rottenrow, Glasgow G4 0NG, UK.
>     +44 141 548 2325, benjamin.hourahine at strath.ac.uk
>
> 2013/4 THE Awards Entrepreneurial University of the Year
>       2012/13 THE Awards UK University of the Year
>
>    The University of Strathclyde is a charitable body,
>         registered in Scotland, number SC015263
>
> _______________________________________________
> 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
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