Specific meaning of the eps0 in the o.eps* file.

[Guangfu Luo]

Dear friends,

After a LDA/GW/BSE optical calculation, one can find two dielectric function in the o.eps* file: eps and eps0. The eps is result of the LDA/GW/BSE calculation, but the meaning of eps0 is kind of ambiguous. This issue has been mentioned in several places [www.yambo-code.org/forum/viewtopic.php?f=13&t=183, viewtopic.php?f=14&t=73, and Computer Physics Communications 180,1392 (2009) ], but for the eps0 at the BSE level, none of the above references stated it specifically enough, in my opinion.

So I did several tests and got the following conclusion: In a LDA/GW calculation, the eps0 corresponds to the LDA/GW without Local Effects (NGsBlkXs=1); In a BSE calculation, the eps0 corresponds to the GW without Local Effects.

Hope this will help other green hand of Yambo.

Sincerely,

[andrea marini]

So I did several tests and got the following conclusion: In a LDA/GW calculation, the eps0 corresponds to the LDA/GW without Local Effects (NGsBlkXs=1); In a BSE calculation, the eps0 corresponds to the GW without Local Effects.

To be more precise. eps0 is the independent particle (IP) absorption without local field effects. But it is the GW IP absorption only if you are providing GW corrections in the input file. If you are not using any QP correction eps0 is the DFT IP absorption.

Andrea