Induced density

[csk]

Dear all!

I am trying to compute the induced density in a metal slab, which I ultimately want in the direction perpendicular to the slab, i.e. integrated over the two periodic directions. To this end, I compute the RPA response function and get the real- and imaginary part of alpha. Now, the induced density (in linear order) should be the integral over the ground state density and the density-density response function. Is there a possibility how I can get the latter in real-space from Yambo?

Many thanks,
Christian

[Davide Sangalli]

Dear Christian,
yambo can give you the response function in G-space. X_{G,G'}(q,\omega)
Page 7 here: https://wiki.yambo-code.eu/wiki/index.p ... heatsheets --> https://wiki.yambo-code.eu/wiki/index.p ... 5.0_P7.png

What you probably (?) want is the induced density
rho_G(q,\omega) = sum_G' X_{G,G'}(q,\omega) V^{ext}_{G'}(q,\omega)

If you are fine with the q=0 and \omega=0 the info you need is printed in the database of the screening ndb.em1s_fragment_1.
Probably with yambopy you can try to code the above equation by reading the ndb.em1s_fragment_1 or similar.

Best,
D.

[csk]

Dear Davide!

Many thanks for your reply!

1) What runlevel would I need such that ndb.em1s* are stored? With "yambo -o c -k Hartree -r" only the dipoles and RIM/cutoff are stored.

2) Can I also access the X_{G,G'}(q,\omega) elements for \omega > 0? If I understand correctly, those are controlled by "ETStpsXd" and "EnRngeXd"?

Cheers,
Christian

[Davide Sangalli]

For the static screening:

Code: Select all

yambo -X b

https://wiki.yambo-code.eu/wiki/index.p ... _screening

If you want the frequency dependent screening use either multi-plasmon pole (MPA) or full freqeuncy (FF)

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yambo -X d / PA

https://wiki.yambo-code.eu/wiki/index.p ... tion_(MPA)

Pleas notice that, however it is not directly the reponse function which is written in the databases, but v(G)*X_{G,G'} (if I'm not wrong), both in the static and in the dynamical case

There is in principle also the option

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yambo -X X

which directly prints the response function, but it is not very much tested.

Best,
D.

[Daniele Varsano]

Dear Christian,

just a small warning. In metals, in the long range limit q->0 intraband contribution to the response functions are not taken into account, while they are for finite q. What you can do is to extrapolate the q->0 limit from the calculated values at finite q.

Best,
Daniele