Yambo Community Forum

Dear all,

I am now trying to compute linear response on semi-metal.
And I want to use the XfnQP_E to do some corrections on the band edge.
I know for semiconductor/ insulator, aaaaa will open the gap while bbbbb and ccccc will stretch the conduction/valance band respectively with the band edge maintained.

However, what if I work on the semi-metal?
There is no well-defined conduction/valance band.
Further stretching and moving the metallic bands may change the occupation for each k-point.

So how does yambo do scissor correction for semi-metal?
And is there a way for me to find the number of the correction?
or a way to plot the scissor corrected band out?

Thank you.

Best
Hsiao-Yi Chen

RIKEN Center for Emergent Matter Science (CEMS),
Wako, Saitama, Japan

Dear Hsiao-Yi Chen,

that variable is meant for semiconductors, you can give it a try using it for semimetal but I'm afraid that it can produce wrong results.

Best,
Daniele

I think you can anyway try to use it. Especially the stretching parameters.
They are defined with respect to the conduction band minimum and valence band maximum which are reported in the report file

For example here In a semi-metal I would expect both to be the same number.
The occupations will be influenced as you say.

You can plot the QP corrected bands using ypp and adding the QP correction variables in input and changing in input

It is not tested, but it may work just fine.

D.

Ciao Daniele, Ciao Davide,

I give a test and plot them.
The operation looks based on the Fermi surface.
So it will cut the metallic bands along Fermi level for rigidly opening a gap.
For the stretching, it also treats the points above fermi as conduction while below fermi as a valance.
So if you use different stretching values to v/c, the result will be very weird.
But if the parameters are the same, it would work pretty well.

BTW,
I remember you can generate QP manually by ypp -q g.
But it was reported with bugs a long time ago.
Is that fixed in some version?


Best
Hsiao-Yi Chen

RIKEN Center for Emergent Matter Science (CEMS),
Wako, Saitama, Japan

Dear Hsiao,

the QP database generator (ypp -q g) it is not much tested and used, anyway it should work.
You can give a try and report if something does not work.
Best,
Daniele