Re: [SIESTA-L] Band Structure and PDOS results not matching

[Suman Chowdhury]

Dear Nick Papior,

Thank you so so much for your help. Can you help me in this regard about
how I can get the correct coordinates for plotting the band structure??

On Thu, Feb 1, 2018 at 3:56 PM, Nick Papior  wrote:

> If I run your system without performing cell relaxations I find the
> attached eigenvalues (for the Monkhorst-Pack grid).
>
> In this case there is *only* a bandgab of ~0.5 eV. Provided that the
> cell-relaxation does not change the spectrum drastically then this is what
> you should suspect in the PDOS.
> Secondly, the PDOS is *exactly* reproducing the bandgab in this
> calculation.
>
> 1) I would highly suggest you to perform cell/coordinate relaxations in
> one directory, then afterwards perform analysis on the relaxed structure,
> PDOS, band-structure, optical, etc.
> 2) Possibly your band-structure coordinates are wrong because when I plot
> the bandstructure for this structure it does not capture the correct band
> gab (this *has* to be the problem).
>
> 2018-01-31 16:35 GMT+01:00 Suman Chowdhury :
>
>> I have just tried to see the variation of TDOS by changing the smearing
>> parameter. But I could not observe any change in it.
>>
>> On Wed, Jan 31, 2018 at 6:44 PM, Suman Chowdhury <
>> sumanchowdhur...@gmail.com> wrote:
>>
>>> This is the fdf that I have used...
>>>
>>> On Thu, Jan 25, 2018 at 11:40 AM, Nick Papior 
>>> wrote:
>>>
 Dear Suman,

 Without data (plots) or fdf file it is very difficult to help you.
 It could be that your smearing parameter is too large.


 2018-01-24 15:13 GMT+01:00 Suman Chowdhury 
 :

> Dear SIESTA User,
>
> Recently I am getting some confusing results by using SIESTA. While
> plotting a band structure I am getting a band gap which is quite large.
> However, when I am trying to plot its corresponding total partial density
> of states (PDOS), I can clearly see that there is no existence of any band
> gap. But interestingly the component PDOS are giving the required band 
> gap.
> The problem is with the total PDOS. Do any of you have any idea about 
> these
> kinds of results...
>
> --
> *Dr. Suman Chowdhury*
>
>
>
> *Assistant Professor Dept. of Physics, Bangabasi College Kolkata-
> 79, West Bengal, India.*
>
>


 --
 Kind regards Nick

>>>
>>>
>>>
>>> --
>>> *Dr. Suman Chowdhury*
>>>
>>>
>>>
>>> *Assistant Professor Dept. of Physics, Bangabasi College Kolkata-
>>> 79, West Bengal, India.*
>>>
>>>
>>>
>>
>>
>> --
>> *Dr. Suman Chowdhury*
>>
>>
>>
>> *Assistant Professor Dept. of Physics, Bangabasi College Kolkata- 79,
>> West Bengal, India.*
>> * Ph no-+91-9830512232 <+91%2098305%2012232>*
>>
>>
>
>
> --
> Kind regards Nick
>



-- 
*Dr. Suman Chowdhury*



*Assistant Professor Dept. of Physics, Bangabasi College Kolkata- 79,
West Bengal, India.*
* Ph no-+91-9830512232*

Re: [SIESTA-L] wsf.band.max problem

[KAREEKUNNAN Afsal]

Dear Maryam Jamaati, 

It is specified by putting the number of highest band you need to calculate 
fatbands. An example is given below. 

WFS.Write.For.Bands .true. 
WFS.Band.Min 1 
WFS.Band.Max 10 

This gives the information for bands from 1 to 10. Note that WFS.Band.Min 
represent the band with lowest energy. 

You may also refer to this tutorial by Prof. Javier Junquera on fatbands. 

http://personales.unican.es/junqueraj/JavierJunquera_files/Metodos/Structuralproperties/Fatbands-SrTiO3/Exercise-Fatbands-SrTiO3.pdf
 

For more tutorials, refer to his page 

http://personales.unican.es/junqueraj/JavierJunquera_files/Metodos/Hands-on-session.html
 

Thanks & Regards 
Afsal 


From: "maryam jamaati"  
To: siesta-l@uam.es 
Sent: Friday, February 2, 2018 1:48:49 AM 
Subject: [SIESTA-L] wsf.band.max problem 

Dear siesta users, 
How we can specify number of wfs.band.max for calculation of fatband? 

sincerely yours, 

maryam jamaati 

Re: [SIESTA-L] Bands at lower energies

[Nick Papior]

A Fermi level is *only* well defined for metallic systems where there are
no band-gabs. When determining the Fermi level for gabbed materials it may
be arbitrarily chosen in the gabbed region.

Often one chooses the fermi level to lie *exactly* in the middle of the
gab. However you have to manually shift the energies in the band-structure.

Note that the important thing is that the number of electrons at the Fermi
level corresponds to the valence charge. With this in mind it should be
clear why the fermi level cannot be uniquely determined for gabbed
materials.

2018-02-01 9:12 GMT+01:00 Sunetra Das :

> Dear all Siesta users,
>
> I am trying to calculate and reproduce the band structure for a certain 2D
> system. The band structure of the system has already been calculated using
> a different software and published. Even though the band structure remains
> the same when calculated using Siesta, the bands are forming at lower
> energy values with respect to the Fermi level.
> How to correct this mismatch and get the bands at their correct energies?
> In my calculation the Fermi level lies near the conduction band whereas in
> the already published data the Fermi level lies very close to the valence
> band. Is there any way to correct for this discrepancy?
> The calculations have been performaned in GGA-PBE exchange correlation
> functional as was done in published data.
> Any suggestion is humbly appreciated.
>
> Thankfully,
> Sunetra Das.
>



-- 
Kind regards Nick

Re: [SIESTA-L] Bands at lower energies

[I. Camps]

You can't change/fix were the Fermi level is. The Fermi level is the
electron chemical potential, so it depends on the number of electrons in
the system.

What some people does is to "normalize" it to zero, but this doesn't change
its  relative position to the bands.

They only thing that occurs now is doing a polarized calculation (as it
treat the electrons with different spins, different).

Em qui, 1 de fev de 2018 19:07, Sunetra Das 
escreveu:

> Dear all Siesta users,
>
> I am trying to calculate and reproduce the band structure for a certain 2D
> system. The band structure of the system has already been calculated using
> a different software and published. Even though the band structure remains
> the same when calculated using Siesta, the bands are forming at lower
> energy values with respect to the Fermi level.
> How to correct this mismatch and get the bands at their correct energies?
> In my calculation the Fermi level lies near the conduction band whereas in
> the already published data the Fermi level lies very close to the valence
> band. Is there any way to correct for this discrepancy?
> The calculations have been performaned in GGA-PBE exchange correlation
> functional as was done in published data.
> Any suggestion is humbly appreciated.
>
> Thankfully,
> Sunetra Das.
>


-- 

[]`s

Camps

Re: [SIESTA-L] Bands at lower energies

[KAREEKUNNAN Afsal]

Dear Sunetra Das, 

>From your mail I understand that the system is a semiconductor. So, from my 
>understanding, as far as the Fermi level lies in the gap (between valence and 
>conduction band), the difference really does not matter. Since in both your 
>case and in the published case, the Fermi level is in the gap, it will not 
>make any difference to the physical properties such as DoS. 

Thanks & Regards 
Afsal 


From: "Sunetra Das"  
To: siesta-l@uam.es 
Sent: Thursday, February 1, 2018 5:12:40 PM 
Subject: [SIESTA-L] Bands at lower energies 

Dear all Siesta users, 

I am trying to calculate and reproduce the band structure for a certain 2D 
system. The band structure of the system has already been calculated using a 
different software and published. Even though the band structure remains the 
same when calculated using Siesta, the bands are forming at lower energy values 
with respect to the Fermi level. 
How to correct this mismatch and get the bands at their correct energies? In my 
calculation the Fermi level lies near the conduction band whereas in the 
already published data the Fermi level lies very close to the valence band. Is 
there any way to correct for this discrepancy? 
The calculations have been performaned in GGA-PBE exchange correlation 
functional as was done in published data. 
Any suggestion is humbly appreciated. 

Thankfully, 
Sunetra Das.