Page 1 of 1
How it works the Quasi-Particle shift?
Posted: Mon Mar 17, 2014 1:32 pm
by javad
Dear developers
I'm trying to do a calculation of optics with a GW-shift,
I have done
yambo -o c -V QP
I got in the input
% XfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP Xd] E parameters (c/v) eV|adim|adim
%
I understood that the first number is the correction to the gap, what are the other two numbers? and how can I use them?
with best regards
Javad Exirifard
Re: How it works the Quasi-Particle shift?
Posted: Mon Mar 17, 2014 1:53 pm
by Daniele Varsano
Dear Javad,
I'm trying to do a calculation of optics with a GW-shift,
I have done
yambo -o c -V QP
OK, but be careful, if you do a linear response calcualtion (RPA) applying a QP shift it is not totally consistent, the QP correction is meant for a BS calculation.
I got in the input
% XfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP Xd] E parameters (c/v) eV|adim|adim
%
I understood that the first number is the correction to the gap, what are the other two numbers? and how can I use them?
The other two variable refers to the slope of the valence/conductions QP energies (coming from a GW calculations for isntances) with respect the KS energies. You can fit them by plotting E_qp vs E_lda. Sometimes beside the QP shift you have a different slope for valence and conduction energies. Considering
you apply only the shift and it is the so called scissor operator approximation.
See
here for a description:
If you cannot apply a simple shift (as for instances in many molecules), you need to calculate the QP energies you need and apply them using the
Qpdb variable with the syntax:
here (n) is if you linked with the netcdf libraries.
Hope it helps,
Best,
Daniele