I am trying to calculate the X-ray absorption spectra using the Real Time Time Dependet-DFT (Real time TDDFT) in the new Qchem version 5.0. I followed the instructions of the manual " url=" , but i don't get any spectra at all.

Basically, a plot the sum of the imaginary parts of the Fourier transform of the dipole moment against the time:

plot(w, w*sum(Im[a(x)] + Im[a(y)] + Im[a(z)])

... but I got a trend which doesn't look like a spectra, becasue it has still negative values.


s= w*Im[a]

then the spectra is

A = (s(xx) + s(yy) +s (zz) )/3

k= kick direction, x,y, or z
s= cross section
A= absorption spectra

Does anybody have any idea hot to get spectra with real time TDDFT?
Any help would be more than appreciated.