[QE-users] How to obtain fermi energy through pDOS calculation of quantum espresso?

[Stefano Baroni]

Dear Moon: there is no point in using any smearing in an insulator (but for plotting the DOS, possibly, but that would be for post-processing purposes only). In order to compute the DOS, you may want to try the tetrahedron method, which is implemented in QE, although I do not know exactly how … Otherwise, Gaussian (or any other smearing) would do, but only in the post-processing phase … HTH — SB


> On 7 Aug 2018, at 09:59, 문태환 <th4512 at cau.ac.kr> wrote:
> 
> Dear Stefano,
> 
> Your advice has helped a lot.
> 
> If I can ask you one more question, can I calculate the fermi energy for semiconductor material if I use DOS calculations using 'gaussian smearing' instead of 'occupations = fixed'?
> 
> Thank you again.
> 
> 
> Moon Taehwan, chung-ang university
> 보낸 사람: Stefano Baroni <baroni at sissa.it <mailto:baroni at sissa.it>> 대신 users <users-bounces at lists.quantum-espresso.org <mailto:users-bounces at lists.quantum-espresso.org>>
> 보낸 날짜: 2018년 8월 7일 화요일 오후 4:42:30
> 받는 사람: Quantum Espresso users Forum
> 제목: Re: [QE-users] How to obtain fermi energy through pDOS calculation of quantum espresso?
>  
> Hi ???,
> 
> The energy zero in any infinite system is arbitrary. In the lack of a surface, only energy differences matter. 
> The zero-temperature Fermi energy of an insulator is also arbitrary, though usually assumed to lie at the middle of the gap.
> 
> Hope this helps.
> 
> Meanwhile, would you mind signing your posts with your name and affiliation?
> 
> Thanks — Stefano B
> 
>> On 7 Aug 2018, at 09:17, 문태환 <th4512 at cau.ac.kr <mailto:th4512 at cau.ac.kr>> wrote:
>> 
>> Hello. I am a beginner to try DFT calculations using quantum espresso (GUI BURAI) for the first time.
>> An attempt was made to calculate the SCF and pDOS using the CIF-file of the organic-inorganic hybrid material (eg MAPbI3). I wanted to get the fermi energy, but I could not find it in the output file of nscf, dos, pdos, scf, etc. because I was immature and calculated occupation as 'fixed'.
>> The problem is that the energy of HOMO and LUMO is calculated as about 1.1 eV and 4.4 eV, and I want to know what is the criterion of 0 eV.
>> 
>> If I use the gaussian smearing method, can I get the correct fermi energy?
>> 
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> — 
> Stefano Baroni -  SISSA, Trieste - http://stefano.baroni.me <http://stefano.baroni.me/>, stefanobaroni (Skype) 
> 
> If the prediction that an airplane can stay up depends on the difference between Riemann and Lebesgue integration, I don’t want to fly in it [Richard W. Hammings]
> 
> 
> 
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— 
Stefano Baroni - Trieste —  http://stefano.baroni.me <http://stefano.baroni.me/> 




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