gmx velacc [-f [<.trr/.cpt/...>]] [-s [<.tpr/.gro/...>]] [-n [<.ndx>]] [-o [<.xvg>]] [-os [<.xvg>]] [-b <time>] [-e <time>] [-dt <time>] [-[no]w] [-xvg <enum>] [-[no]m] [-[no]recip] [-[no]mol] [-acflen <int>] [-[no]normalize] [-P <enum>] [-fitfn <enum>] [-beginfit <real>] [-endfit <real>]
gmx velacc computes the velocity autocorrelation function. When the -m option is used, the momentum autocorrelation function is calculated.
With option -mol the velocity autocorrelation function of molecules is calculated. In this case the index group should consist of molecule numbers instead of atom numbers.
Be sure that your trajectory contains frames with velocity information (i.e. nstvout was set in your original .mdp file), and that the time interval between data collection points is much shorter than the time scale of the autocorrelation.
Options to specify input files:
Options to specify output files:
Other options: