[Pw_forum] band gap from hybrid pseudopotentials

[MSaqlain]

Dear Evan

Thanks for your explanation



On 08/05/2016 06:45 PM, 毛飞 wrote:
>
> 在2016-08-05，saqlain <saqlain at bilkent.edu.tr> 写道:
>
>     -----原始邮件-----
>     *发件人:* saqlain <saqlain at bilkent.edu.tr>
>     *发送时间:* 2016年8月5日 星期五
>     *收件人:* PWSCF Forum <pw_forum at pwscf.org>
>     *主题:* Re: [Pw_forum] band gap from hybrid pseudopotentials
>
>     Dear Evan
>
>     Thanks for your reply. However, I still have some confusions, if
>     you can help to resolve these.
>
>     1. I have not use smearing in the calculations. What happens if
>     smearing is used? I haven't yet understood how to get Fermi
>     energy. The output file is attached, if you can help me figure out
>     the value and the procedure to see this value
>
>     You can get the Fermi energy of your system when you add some
>     smearing in the scf calculation.
>
>     2. When I use plotbands.x it asks a few questions, can you tell me
>     what is meaning of this question {deltaE, reference E (for tics)}
>
>     I think these questions are self-explantory, deltaE is the
>     distance of the adjant two points in the band structure, for
>     reference E, you can put the maximum of the valence band, then the
>     maximum valence band is shifted to 0 eV in the plot. you can
>     follow some
>     tutorials:http://www.fisica.uniud.it/~giannozz/QE-Tutorial/
>
>     3. What are these values? and where would these are to be used?
>
>     high-symmetry point:  0.0000 0.0000 0.0000   x coordinate 0.0000
>     high-symmetry point: -0.0016 0.0000 0.0856   x coordinate 0.0857
>     high-symmetry point: -0.0016 0.0861 0.0856   x coordinate 0.1718
>     high-symmetry point:  0.0841 0.0861 0.0840   x coordinate 0.2575
>     high-symmetry point:  0.0857 0.0861-0.0016   x coordinate 0.3432
>     high-symmetry point:  0.0000 0.0861 0.0000   x coordinate 0.4289
>     high-symmetry point:  0.0857 0.0000-0.0016   x coordinate 0.5504
>     high-symmetry point:  0.0841 0.0000 0.0840   x coordinate 0.6361
>
>     4. In your message you wrote, band gap = I-A, what is I and A????
>
>     I: Ionization energy; A: Affinity energy
>
>     I am an experimental guy, and have recently joined dft
>     calculations, so have a little idea about these things. extremely
>     sorry for this.
>
>     Cheers
>
>     Msaqlain
>
>
>     On 08/05/2016 06:14 AM, 毛飞 wrote:
>>     Hello, Msaqlain
>>
>>     > -----原始邮件-----
>>     > 发件人: saqlain<saqlain at bilkent.edu.tr>
>>     > 发送时间: 2016年8月5日 星期五
>>     > 收件人:pw_forum at pwscf.org
>>     > 抄送:
>>     > 主题: [Pw_forum] band gap from hybrid pseudopotentials
>>     >
>>     > Dear QE users
>>     >
>>     > I would like to use QE for calculating band gap with hybrid
>>     > pseusopotentials approach.
>>     >
>>     > after going from the discussions available at different sites, I have
>>     > done the calculation in this way: vc-relax the system, did scf and then
>>     > nscf followed by band structure calculation. My questions are,
>>     >
>>     > 1. How can I now extract the band gap from the file generated by bands.x?
>>
>>     The output file generated by bands.x can be processed by
>>     plotbands.x to plot the band structure, then you can obtain the
>>     band gap.
>>
>>     > 2. in the scf and nscf output files, I can't see Fermi energy. How can I
>>     > know about the Fermi energy?
>>
>>     Do you add some smearing in these calculations?
>>
>>     > 3. The scf and nscf files contain, highest occupied and lowest occupied
>>     > levels? what is meaning of this? does the highest occupied level mean
>>     > Fermi energy?
>>
>>     No, for insulators (which shows the electronic band gap), the
>>     Fermi energy stays between the HOMO and LUMO
>>
>>       
>>     > 4. does the difference of highest occupied and lowest occupied level
>>     > correspond to band gap?
>>
>>     No, the band gap Eg = I-A.
>>
>>     regards
>>
>>     evan
>>
>>     > your response would be highly appreciated
>>     >
>>     > Msaqlain
>>     >
>>     > Bilknet, Ankara. Turkey
>>     >
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