Question about compute VACF

Hi everyone,

There are 4 terms in the output of VACF computing style. The 4th term is the total VACF. I don’t understand why it directly sums the other 3 terms up.
If I want to calculate total vibration spectrum or total phonon density of state. Can I just simply apply FFT to the 4th term of the output?
Thank you very much.

Sincerely,
Yuan

Not sure what you are asking. The doc page says what
the 4 outputs are, and you can look at the source
code in compute_vacf.cpp if you are unsure.

They are the VACF at a point in time, relative to
a time origin.

How you use those outputs is up to you.

The compute vacf doc page gives one example,
e.g. to time integrate them for a diffusion coeff.

Steve