Autocorrelation function

LAMMPS LAMMPS Development
1

Hello,

I just started with the molecular dynamics code LAMMPS 2 months ago.
Among the commands that this code offers, there is one that calculates the velocity autocorrelation function (VACF). I would rather have the autocorrelation function of the positions which is not implemented in the code.
Is it possible to include a package for this? If yes, how can I do it?

Best regard,
LM

3

Creating a variant of compute vacf that uses the positions instead of velocities should be a rather simple exercise.

Please see:
https://docs.lammps.org/Modify.html

and specifically:
https://docs.lammps.org/Modify_compute.html

You can just copy the existing files to a new name, change the class name and keyword accordingly and then update the internal code. While velocities are stored in the Atom::v arrays, positions are in Atom::x.