Hi all,
I want to calculate k and omegadependent RPA spectral function (which is basically ARPES spectrum). Here kpoints are chosen along the highsymmetry directions of the BZ (like in band structures)
Is it possible in Yambo? How to do it if it is possible?
Best,
Weiqing
RPA spectral function
Moderators: Davide Sangalli, andrea marini, Conor Hogan, myrta gruning

 Posts: 48
 Joined: Thu Sep 06, 2018 7:57 am
 Location: Wuhan University
RPA spectral function
Weiqing Zhou
Phd student
Wuhan University
Wuhan, Hubei, 430072
Phd student
Wuhan University
Wuhan, Hubei, 430072
 Davide Sangalli
 Posts: 318
 Joined: Tue May 29, 2012 4:49 pm
 Location: Via Salaria Km 29.3, CP 10, 00016, Monterotondo Stazione, Italy
 Contact:
Re: RPA spectral function
Dear Weiqing,
in ARPES you measure the bands, so the output of a GW calculation gives you the eigenvalues and also the related width (imaginary part of the self energy).
From that you can construct the ARPES signal in the QP approximation (i.e. only QP peaks available).
If you want to go beyond, you can set the Dyson solver to "g" in the input file for a GW calculation.
The output will be a frequency dependent spectral function for each band and each kpoint.
There you would also get satellites, although probably not always in the right place, as discussed in recent works in the literature.
Is this what you mean when you write "RPA spectral function" ?
Hope it helps.
Best,
D.
in ARPES you measure the bands, so the output of a GW calculation gives you the eigenvalues and also the related width (imaginary part of the self energy).
From that you can construct the ARPES signal in the QP approximation (i.e. only QP peaks available).
If you want to go beyond, you can set the Dyson solver to "g" in the input file for a GW calculation.
The output will be a frequency dependent spectral function for each band and each kpoint.
There you would also get satellites, although probably not always in the right place, as discussed in recent works in the literature.
Is this what you mean when you write "RPA spectral function" ?
Hope it helps.
Best,
D.
Davide Sangalli, PhD
CNRISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davidesangallicv/
http://www.maxcentre.eu/
CNRISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davidesangallicv/
http://www.maxcentre.eu/

 Posts: 48
 Joined: Thu Sep 06, 2018 7:57 am
 Location: Wuhan University
Re: RPA spectral function
Dear Davide,
Thanks for your reply.
1. In GW calculation(with g n), the output is
Kpoint Band Eo E EEo DFT HF ScEo ScE dSc/dwEo Z(Re) Z(Im) Width[meV] Width[fs]
#
1.000 3.000 .7424 1.782 1.040 23.11 28.94 4.561 4.783 .2136 0.8240 .1338E2 17.75 37.08
1.000 4.000 .7424 1.820 1.078 23.11 28.94 4.517 4.747 .2134 0.8241 .1335E2 17.70 37.18
Actually, I don't understand the meaning of some column, f.e ScEo, dSc/dwEo and Width.
Q1 : What is the meaning of them? And what is the definition of width?
2. Indeed, I can obtain the frequencydependent Green's function in realaxis GW calculaton (d g g) and the output like :
Energy Re[G] Im(G) Re(S_tot) Im(S_c) Re(S_c)
5.742438 .4152761 0.3928327E2 2.592178 0.2277692E1 3.230304
5.742138 .4153412 0.3929308E2 2.592256 0.2277546E1 3.230226
Q2 : Is Re[G] the real part of Green's function (Im(G) for the Imaginary part )? And what is the meaning of Re(S_tot),Im(S_c) and Re(S_c)?
3. From Yambo Tutorials, I understand that PPA, COHSEX and realaixs are implemented in GW calculation.
Q3 : can I do a GW calculation within Random Phase Approximation instead of PPA or COHSEX?
4. I want to do a GW calculation along a chosen k path, which is not uniform. From Tutorials, a new set of kpoints containing chosen ones can be generated by BZ kpoint grid generator in ypp (ypp k k). But when I add three new kpoints into the list like:
%GWKpts # K points list
0.00000 0.50000 0.00000
0.00000 0.48979 0.00000
0.00000 0.47959 0.00000
%
Only the 3rd point is in the new set of kpoints.
Q4 : Can I generate a new set of kpoints with more than one chosen point in ypp?
Best,
Weiqing
Thanks for your reply.
1. In GW calculation(with g n), the output is
Kpoint Band Eo E EEo DFT HF ScEo ScE dSc/dwEo Z(Re) Z(Im) Width[meV] Width[fs]
#
1.000 3.000 .7424 1.782 1.040 23.11 28.94 4.561 4.783 .2136 0.8240 .1338E2 17.75 37.08
1.000 4.000 .7424 1.820 1.078 23.11 28.94 4.517 4.747 .2134 0.8241 .1335E2 17.70 37.18
Actually, I don't understand the meaning of some column, f.e ScEo, dSc/dwEo and Width.
Q1 : What is the meaning of them? And what is the definition of width?
2. Indeed, I can obtain the frequencydependent Green's function in realaxis GW calculaton (d g g) and the output like :
Energy Re[G] Im(G) Re(S_tot) Im(S_c) Re(S_c)
5.742438 .4152761 0.3928327E2 2.592178 0.2277692E1 3.230304
5.742138 .4153412 0.3929308E2 2.592256 0.2277546E1 3.230226
Q2 : Is Re[G] the real part of Green's function (Im(G) for the Imaginary part )? And what is the meaning of Re(S_tot),Im(S_c) and Re(S_c)?
3. From Yambo Tutorials, I understand that PPA, COHSEX and realaixs are implemented in GW calculation.
Q3 : can I do a GW calculation within Random Phase Approximation instead of PPA or COHSEX?
4. I want to do a GW calculation along a chosen k path, which is not uniform. From Tutorials, a new set of kpoints containing chosen ones can be generated by BZ kpoint grid generator in ypp (ypp k k). But when I add three new kpoints into the list like:
%GWKpts # K points list
0.00000 0.50000 0.00000
0.00000 0.48979 0.00000
0.00000 0.47959 0.00000
%
Only the 3rd point is in the new set of kpoints.
Q4 : Can I generate a new set of kpoints with more than one chosen point in ypp?
Best,
Weiqing
Weiqing Zhou
Phd student
Wuhan University
Wuhan, Hubei, 430072
Phd student
Wuhan University
Wuhan, Hubei, 430072
 Davide Sangalli
 Posts: 318
 Joined: Tue May 29, 2012 4:49 pm
 Location: Via Salaria Km 29.3, CP 10, 00016, Monterotondo Stazione, Italy
 Contact:
Re: RPA spectral function
Width is the imaginary part of the selfenergyThanks for your reply.
1. In GW calculation(with g n), the output is
Kpoint Band Eo E EEo DFT HF Sc Eo ScE dSc/dwEo
#
1.000 3.000 .7424 1.782 1.040 23.11 28.94 4.561 4.783 .2136
1.000 4.000 .7424 1.820 1.078 23.11 28.94 4.517 4.747 .2134 0.8241 .1335E2 17.70 37.18
Actually, I don't understand the meaning of some column, f.e ScEo, dSc/dwEo and Width.
Q1 : What is the meaning of them? And what is the definition of width?
Z is the renormalization factor (you find the definition in MBPT books)
Sc is the real part of the correlation selfenergy
The E or Eo in front I think depends it they are evaluated at the bare or at the QP pole(not sure)
S_tot is the total selfenergy, S_c the correlation part2. Indeed, I can obtain the frequencydependent Green's function in realaxis GW calculaton (d g g) and the output like :
Energy Re[G] Im(G) Re(S_tot) Im(S_c) Re(S_c)
5.742438 .4152761 0.3928327E2 2.592178 0.2277692E1 3.230304
5.742138 .4153412 0.3929308E2 2.592256 0.2277546E1 3.230226
Q2 : Is Re[G] the real part of Green's function (Im(G) for the Imaginary part )? And what is the meaning of Re(S_tot),Im(S_c) and Re(S_c)?
If I undertand what you mean, RPA is what is yambo si called realaxis, i.e. byond PPA.3. From Yambo Tutorials, I understand that PPA, COHSEX and realaixs are implemented in GW calculation.
Q3 : can I do a GW calculation within Random Phase Approximation instead of PPA or COHSEX?
You do not put p p nor p c when generating the input
Yeah, you should be able.4. I want to do a GW calculation along a chosen k path, which is not uniform. From Tutorials, a new set of kpoints containing chosen ones can be generated by BZ kpoint grid generator in ypp (ypp k k). But when I add three new kpoints into the list like:
%GWKpts # K points list
0.00000 0.50000 0.00000
0.00000 0.48979 0.00000
0.00000 0.47959 0.00000
%
Only the 3rd point is in the new set of kpoints.
Q4 : Can I generate a new set of kpoints with more than one chosen point in ypp?
I'm not ure hat is happening here.
Best,
D.
Davide Sangalli, PhD
CNRISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davidesangallicv/
http://www.maxcentre.eu/
CNRISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davidesangallicv/
http://www.maxcentre.eu/