Confusing about QPkrange

[lesheng]

Hi all,

In the document, it says QPkrange selects the matrix elements to calculate. But how can I understand the kpoint and band index here? And is it necessary to do convergence test on QPkrange? Is there any relationship between this band index here and the one from BndsRxXp or GbndRnge?

Thanks,
Lesheng Li

[Daniele Varsano]

Dear Lesheng,
these are the index of the k-points and bands you want to calculate the GW corrections. For instance if you want to calculate the first 4 bands at gamma point, it will be :

Code: Select all

%QPkrange				
1| 1| 1| 4|		#	(GW)	 QP generalized Kpoint/Band indices
%

The index of each k point is reported in the setup report.
Best,
Daniele

[lesheng]

Dear Lesheng,
these are the index of the k-points and bands you want to calculate the GW corrections. For instance if you want to calculate the first 4 bands at gamma point, it will be :

Code: Select all

%QPkrange				
1| 1| 1| 4|		#	(GW)	 QP generalized Kpoint/Band indices
%

The index of each k point is reported in the setup report.
Best,
Daniele

Hi Daniele,

Thanks for your reply. My confusing is the band index in this variable.

Say I have a system with 10 electrons, and I'm interested in gamma point, so the QPkrange should be

1|1|1|x|

and if the "x" here is set to be 5, does it mean the quasi-particle energy of the 6th band or the bands above 5 will be less accurate?

Thanks,
lesheng

[Daniele Varsano]

Dear Lesheng,
it was an example as I do not know on what system you are dealing with.
You can put there the number of band you want (provided that you have calculate that number of bands in the ground state), as you can be interested in both occupied and unoccupied states, for example if you want to calculate the gap. For example you can put |1|1|5|6| if you are interested in the gap only.
Best,
Daniele

[lesheng]

Dear Lesheng,
it was an example as I do not know on what system you are dealing with.
You can put there the number of band you want (provided that you have calculate that number of bands in the ground state), as you can be interested in both occupied and unoccupied states, for example if you want to calculate the gap. For example you can put |1|1|5|6| if you are interested in the gap only.
Best,
Daniele

Hi Daniele,

If I specify it as

1|1|5|6|

Does it mean I will get less accurate results for the other bands (except for 5th and 6th)?

Best,
lesheng

[Daniele Varsano]

Dear Lesheng,
No, it means that you will calculate the GW corrections for the two bands you indicated only.
Daniele

[lesheng]

Dear Lesheng,
No, it means that you will calculate the GW corrections for the two bands you indicated only.
Daniele

Hi Daniele,

I think I understand it after your explanation now. But I just want to make sure I interpret it in the right way. So when I specify it as

1|1|5|6|

it will not affect the accuracy for other bands, because it only calculate 5 and 6. So in the output from my GW calculation, only 5 and 6 has GW correction, is that correct?

Thanks,
lesheng

[Daniele Varsano]

Yes, that's correct!!!
Best,
Daniele

[lesheng]

Yes, that's correct!!!
Best,
Daniele

Thank you very much!

Best,
lesheng