[Pw_forum] Selection of K point for band structure calculation

[Valentina Shvets]

The resource http://materialscloud.org/tools/seekpath/input_structure is
excellent, however, it does not read the files with the extension, *.сif,
which I take from the resource COD (www.crystallography.net). Could you
kindly inform which information and in what format should be entered in the
resource you created to calculate the k-points data required for Quantum
ESPRESSO pw.x input.

With kind regard,

V. Shvets

On Mon, Oct 23, 2017 at 7:22 PM, Saif Ullah <kiterunner7 at gmail.com> wrote:

> How to decide that? For inverse spinel (CuFe2O4) with FCC structure (56
> atoms), what is the minimum number of K point (approx) required?
>
> There is no such thing like minimum or maximum. You need to look at your
> bands. If it is smooth, then the number is fine. To be on a safer side, I
> would recommend 50 along each of the high symmetry points. If your cell is
> too small, then you need to increase and vice versa.
>
> Regards
> Saif
> Department of Physics, UFJF, Brazil
>
> On Mon, Oct 23, 2017 at 2:55 PM, Madhurya Chandel <
> madhurya.svnit at gmail.com> wrote:
>
>> Thank you for your kind reply.
>>
>> The number of points is free, but you have to take it large enough that
>> the bands look smooth and not jagged.
>>
>> How to decide that? For inverse spinel (CuFe2O4) with FCC structure (56
>> atoms), what is the minimium number of K point (approx) required?
>>
>> Also, the continuity analysis done by bands.x
>> what is the continuity analysis?
>>
>>
>>  You just need to go through the high symmetry points. The link may be
>> useful:  http://web.mit.edu/xcrysden_v1.5.60/www/XCRYSDEN/doc/kpath.html)
>> Thank you for your help but I already referred this
>>
>> With regards
>> Madhurya
>>
>>
>> On Mon, Oct 23, 2017 at 6:09 PM, Lorenzo Paulatto <paulatz at gmail.com>
>> wrote:
>>
>>> On 21/10/17 12:59, Madhurya Chandel wrote:
>>>
>>> Respected QE Users
>>>
>>> 1)I have a doubt that how to choose the number of K point for band
>>> structure calculation using Xcysden K path selection?
>>>
>>>
>>> Hello,
>>>
>>> I also recommend trying the seekpath online tool
>>> <http://materialscloud.org/tools/seekpath/input_structure/>
>>> <http://materialscloud.org/tools/seekpath/input_structure/>, it is a
>>> bit easier than xcrysden to use for this task, as it also suggests a
>>> possible choice of path. The number of points is free, but you have to take
>>> it large enough that the bands look smooth and not jagged. Also the
>>> continuity analysis done by bands.x may not work if too few points are
>>> present. Note that if you use the tpiba_b or crystal_b format for the
>>> points, you only need to specify the path high-symmetry turning points, and
>>> the number of k-points in between (check the manual)
>>>
>>> 2) while doing the band structure calculation how to chose Fermi energy
>>> (=  eV), deltaE and reference energy? Do these values affect the band
>>> structure plot?
>>>
>>>
>>> They do not, it is just a rigid shift. It is customary to shift the
>>> bands so that the Fermi energy is at zero. Of course, if your material is
>>> an insulator there is not Fermi energy, if you have empty bands you can
>>> take it in the middle of the gap (average of highest occupied and lowest
>>> unoccupied energy levels). All these values are printed at the end of any
>>> SCF and NSCF (not BANDS) calculation, check the output file.
>>>
>>> hope this helps
>>>
>>>
>>> Thanking you
>>>
>>> With regards
>>>
>>> *Madhurya Chandel*
>>>
>>> *Research Scholar *
>>>
>>> *Department of Chemistry *
>>>
>>> *BITS PILANI, GOA campus *
>>>
>>> *+91-7507546773 <+91%2075075%2046773>*
>>>
>>>
>>> _______________________________________________
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>>>
>>>
>>> --
>>> Lorenzo Paulatto - Paris
>>>
>>>
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>>
>>
>>
>> --
>>
>> *Madhurya Chandel*
>>
>> *Research Scholar *
>>
>> *Department of Chemistry *
>>
>> *BITS PILANI, GOA campus*
>>
>> *+91-7507546773 <+91%2075075%2046773>*
>>
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>>
>
>
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