[lammps-users] anyone up for VACF or power spectra?

I will soon be wanting to generate velocity autocorrelation functions (vacf) from lammps dump files. Has anyone else has done this or knows of some other software to do it?

I think fix_msd would be a great place to start adding vacf functionality in lammps. The velocity binning for a vacf is similar to the displacement binning in msd.

The next step is to Fourier transform the vacf and generate a frequency spectrum. Can fft3d be used for that?



You can use CHARMM to calculate velocity autocorrelation functions if
you convert the LAMMPS velocity dump into a binary file using the script
found in the LAMMPS directory /tools/ch2lmp/other called mkdcd.f.

Here is a link to the CHARMM forum that has a small script on how to
calculate the vacf:

I don't know how to do the frequency spectrum though.

Hope this helps.

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