g_velacc VERSION 3.3_beta_20050823

g_velacc -f traj.trr -s topol.tpr -n index.ndx -o vac.xvg -[no]h -nice int -b time -e time -dt time -[no]w -[no]xvgr -[no]mol -acflen int -[no]normalize -P enum -fitfn enum -ncskip int -beginfit real -endfit real

g_velacc computes the velocity autocorrelation function. When the -s option is used, the momentum autocorrelation function is calculated.

With option -mol the momentum autocorrelation function of molecules is calculated. In this case the index group should consist of molecule numbers instead of atom numbers.

-f traj.trr Input Full precision trajectory: trr trj

-s topol.tpr Input, Opt. Structure+mass(db): tpr tpb tpa gro g96 pdb xml

-n index.ndx Input, Opt. Index file

-o vac.xvg Output xvgr/xmgr file

-[no]h no Print help info and quit

-nice int 19 Set the nicelevel

-b time 0 First frame (ps) to read from trajectory

-e time 0 Last frame (ps) to read from trajectory

-dt time 0 Only use frame when t MOD dt = first time (ps)

-[no]w no View output xvg, xpm, eps and pdb files

-[no]xvgr yes Add specific codes (legends etc.) in the output xvg files for the xmgrace program

-[no]mol no Calculate vac of molecules

-acflen int -1 Length of the ACF, default is half the number of frames

-[no]normalize yes Normalize ACF

-P enum 0 Order of Legendre polynomial for ACF (0 indicates none): 0 , 1 , 2 or 3

-fitfn enum none Fit function: none , exp , aexp , exp_exp , vac , exp5 , exp7 or exp9

-ncskip int 0 Skip N points in the output file of correlation functions

-beginfit real 0 Time where to begin the exponential fit of the correlation function

-endfit real -1 Time where to end the exponential fit of the correlation function, -1 is till the end

gromacs(7)

More information about the GROMACS suite is available in /usr/share/doc/gromacs or at <http://www.gromacs.org/>.