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

[Suman Chowdhury]

Just let me know how did you calculate the DOS..

On Sat, Feb 3, 2018 at 3:04 AM, Nick Papior  wrote:

> Dear Suman,
>
> I think you should solve this yourself.
>
> 2018-02-02 5:56 GMT+01:00 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 <
>> sumanchowdhur...@gmail.com>:
>>
>>> 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 <+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] Bands at lower energies

[Sunetra Das]

Dear All,

Thank you very much for answering my query. I have been trying to reproduce
the TDOS for a reported half metallic system, as well, and the Fermi level
in this case is lying in a region with non-zero DOS for both the spins,
even though the DOS looks the same as reported in published data. Here the
relative positioning of the Fermi level with the bands did change the
nature of the studied structure.
Where am I going wrong? If someone please elaborates this to me, I will be
thankful.

Regards,
Sunetra Das.

On 2 February 2018 at 11:23, Nick Papior  wrote:

> 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
>