[DFTB-Plus-User] Band Gap calculation
Ben Hourahine
benjamin.hourahine at strath.ac.uk
Sun Nov 18 22:04:08 CET 2018
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
> <mailto: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
> <mailto: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 <mailto: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
>> <mailto: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
>>
>> image1.tiff
>>
>> On Nov 4, 2018, at 3:29 PM, Ben Hourahine
>> <benjamin.hourahine at strath.ac.uk
>> <mailto: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
>>>> <mailto: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?
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>
>>> --
>>> 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
>>> <mailto: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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>>
>>
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>
> --
> 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
> <mailto: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
> <mailto:DFTB-Plus-User at mailman.zfn.uni-bremen.de>
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>
>
>
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--
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
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