I try to calculate the ACF ( autocorrelation function) ,such as velocity autocorrelation function from the dump file of LAMMPS. I want to obtain the power spectra from the
ACF, Then I do Frourier transform of ACF. Then I got a spectrum. I think that the unit of the x-axis of the spectrum should be (1/ps), since it is calculated from the Frouries transform of ACF. However, I find that in many papers, that unit is (1/cm), the unit of wavenumber.
Any suggestion is appreciated.