I have basic some questions about TDDFT.

1. I copied a portion of the " subroutine TDDFT_ALDA_G_space(E,k) " of Yambo.5.1.1 , see below:

Code: Select all

```
call XC_potential_driver(E,k,WF_kind,WF_xc_functional,2)
do i1=1,fft_size
F_xc_DP(i1)=sum(cmplx(F_xc(i1,:,:),kind=DP))
enddo
!
! need to reset the plan to do a BACKWARD FFT (R->G)
!
fftw_plan=0
#if defined _FFTW
call fft_3d(F_xc_DP,fft_dim,-1,fftw_plan)
#else
call fft_3d(F_xc_DP,fft_dim,-1)
#endif
!
! F_xc in gspace
!
YAMBO_ALLOC(F_xc_gspace,(FXC_n_g_corr,FXC_n_g_corr,1))
do i1=1,FXC_n_g_corr
do i2=1,FXC_n_g_corr
F_xc_gspace(i1,i2,1)=cmplx(F_xc_DP( fft_g_table( G_m_G(i1,i2),1) ),kind=SP)/real(fft_size,SP)
enddo
enddo
```

or, the " call fft_3d " did the "fft_size" of "F_xc_DP " on G space points, but only " FXC_n_g_corr " number of "F_xc_DP " on G space points is really used eventually?

Please help me understand this.

2. For a TDDFT ALDA run, the EELS output file is "o-alda_q100.eel_q1_inv_alda_dyson", in which the 2nd column is ALDA EELS, what dose the 4th column "EEL_o-Im[4] " mean? is it the TDDFT run with the kernel=0 or so-called TDDFT-Hartree? or, is it the IP (independent particle level calculation, means no Dyson equation for the response function Chi )? Which is for the 4th column?

3. then, I did the same system with TDDFT ALDA, LRC and BSFXC (Chimod= "BSFXC"), from the 3 output EELS data, it shows that the 4th column from ALDA and LRC is almost the same, while the 4th column of BSFXC is very different from the previous two. If the 4th column is IP (independent particle level calculation), then the data from the three kernels should be the same, right?

Does GrFnTpXd= "R" or "T" matter for the 4th column?

I did not set GrFnTpXd for each run, but why GrFnTpXd will goes to different setting automatically?

In a different run (with Drude term), even I set GrFnTpXd= "T" or "r", but it will automatically become GrFnTpXd= "R", why is that?

Please help me.

Best,

Hong