wrong Fermi level??

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wrong Fermi level??

Postby zsjan » Sat Dec 27, 2014 4:08 pm

Dear all:
My PW nscf calculations report that "highest occupied, lowest unoccupied level (ev): 25.9823 25.9261". However, the setup of yambo gives me that"

Fermi Level [ev]: 5.671248
Electronic Temp. [ev K]: 0.00 0.00
Bosonic Temp. [ev K]: 0.00 0.00
El. density [cm-3]: 0.422E+24
States summary : Full Metallic Empty
0001-0108 0109-0500
Indirect Gaps [ev]: 6.297390 6.347350
Direct Gaps [ev]: 6.321119 6.999879
"
my system is under high temperature about 8000K, but the temp reported is 0. Besides, the Fermi level is far more different with that of pw calculations. Why?
Shijun Zhao
College of Engineering
Peking University
zsjan
 
Posts: 26
Joined: Wed Aug 27, 2014 8:09 am

Re: wrong Fermi level??

Postby Daniele Varsano » Sat Dec 27, 2014 4:14 pm

Dear Shijun,
It is very hard to help you if you do not post some useful informations, as yambo report files and Pwscf outputs.
Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
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Re: wrong Fermi level??

Postby zsjan » Sun Dec 28, 2014 2:43 am

Daniele Varsano wrote:Dear Shijun,
It is very hard to help you if you do not post some useful informations, as yambo report files and Pwscf outputs.
Best,
Daniele



Please see the attachment. I have used the occupation_fix options. Maybe it is the problem? If I do not use this option, everything goes well.
Last edited by zsjan on Sun Dec 28, 2014 1:38 pm, edited 1 time in total.
Shijun Zhao
College of Engineering
Peking University
zsjan
 
Posts: 26
Joined: Wed Aug 27, 2014 8:09 am

Re: wrong Fermi level??

Postby Daniele Varsano » Sun Dec 28, 2014 9:01 am

Dear Shijun,
next time please use the upload button to post files as with copy-paste is very hard then to read them.

Yes the problem as you argue is that you used the occupation_fixed options. If you use for instance the occupations='smearing' option the electronic temperature will be then read by yambo and used to calculate the Fermi level. Yambo do recalculate occupations and Femi level, and in this case this was done as at 0K temperature.
Other option would be to add the ElecTemp variable in your setup input file. But I suggest the first method as you are sure everything is consistent.
Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
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Daniele Varsano
 
Posts: 2052
Joined: Tue Mar 17, 2009 2:23 pm

Re: wrong Fermi level??

Postby zsjan » Sun Dec 28, 2014 1:41 pm

Daniele Varsano wrote:Dear Shijun,
next time please use the upload button to post files as with copy-paste is very hard then to read them.

Yes the problem as you argue is that you used the occupation_fixed options. If you use for instance the occupations='smearing' option the electronic temperature will be then read by yambo and used to calculate the Fermi level. Yambo do recalculate occupations and Femi level, and in this case this was done as at 0K temperature.
Other option would be to add the ElecTemp variable in your setup input file. But I suggest the first method as you are sure everything is consistent.
Best,
Daniele



Thank you very much. So how the yambo recalculate the occupations and Fermi level? Is this according to Fermi-dirac distribution or something?
If I want to assign certain occupations to initialize the calculations, what can i do to acheive this?
Shijun Zhao
College of Engineering
Peking University
zsjan
 
Posts: 26
Joined: Wed Aug 27, 2014 8:09 am

Re: wrong Fermi level??

Postby Daniele Varsano » Sun Dec 28, 2014 1:59 pm

. So how the yambo recalculate the occupations and Fermi level? Is this according to Fermi-dirac distribution or something?

Yes, they are calculated according to the Fermi-Dirac distribution.
If I want to assign certain occupations to initialize the calculations, what can i do to acheive this?

What you can do, is to play with electronic temperature, but you cannot fix occupations by hand.

Hope it helps,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
User avatar
Daniele Varsano
 
Posts: 2052
Joined: Tue Mar 17, 2009 2:23 pm


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