Yambo Community Forum

Dear Yambo masters,

I am using Yambo 5.1.1 and trying to put into a frequency dependent tddft kernel (home made).
I have a basic question about the subroutine TDDFT_ALDA_G_space(E,k).

1. As I understand, the subroutine TDDFT_ALDA_G_space(E,k) is frequency independent. It only calculates the F_xc_gspace(i1,i2,1) for the one frequency point (which is zero). Since F_xc_gspace is allocated as " YAMBO_ALLOC(F_xc_gspace,(FXC_n_g_corr,FXC_n_g_corr,1)) ".
Is this understanding correct?

2. the subroutine TDDFT_ALDA_G_space(E,k) is also q independent. Although we can input different q by using " % QpntsRXd
1 | 1 | # [Xd] Transferred momenta
% " ,
however, subroutine TDDFT_ALDA_G_space(E,k) will calculate and get the same F_xc_gspace(i1,i2,1) for different q.
Is this understanding correct?

3. if I modify subroutine TDDFT_ALDA_G_space(E,k) as subroutine tddft_alda_g_space(E,k,iq,wv) ,
where iq for the index of q, and wv for the frequency. iq is just an integer, for optic calculations, iq=1.

for wv, I use " type(w_samp) :: wv ".
then I do " allocate(F_xc_gspace(FXC_n_g_corr,FXC_n_g_corr,wv%n_freqs)) " to make F_xc_gspace includes all the frequency points.

I understand iq and wv will get values from the subroutine who calls " tddft_alda_g_space(E,k,iq,wv) ". However, in order to be easy to do the calculations for F_xc_gspace in subroutine tddft_alda_g_space(E,k,iq,wv), I read the " % EnRngeXd " and " ETStpsXd= " from the input file, and let the real (not complex) frequency points be calculated in the subroutine tddft_alda_g_space(E,k,iq,wv), then I calculate the F_xc_gspace for each real frequency point in the subroutine tddft_alda_g_space(E,k,iq,wv).

Then, once the call for subroutine tddft_alda_g_space(E,k,iq,wv) is done, I got the needed F_xc_gspace(FXC_n_g_corr,FXC_n_g_corr,wv%n_freqs) for all frequency points.

Then, the rest code will calculate the optic properties (such as eels) with the frequency dependent tddft kernel.

Is the above processing correct?

Please help me!

I appreciate your help very much!


Best,
Hong

Dear Hong,
I'd say all you wrote is correct.

After you generate your frequency dependent Fxc you just need to change the call inside X_redux, and put the proper frequency index.
You might need to pay attention to the parallelization in case the code is parallelized over frequencies.

Best,
D.