[DFTB-Plus-User] Band Gap calculation

Sarah Gamal s.abouelhasab at gmail.com
Fri Nov 23 12:00:24 CET 2018 

What do you think?

On Tue, Nov 20, 2018 at 8:12 PM Sarah Gamal <s.abouelhasab at gmail.com> wrote:

> 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
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>>>>>>
>>>>>> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
>>>>>>
>>>>>>
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>>>> 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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