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GMX-RMSDIST(1)			     GROMACS			  GMX-RMSDIST(1)

NAME
     gmx-rmsdist  -  Calculate atom pair distances averaged with power -2, -3 or
     -6

SYNOPSIS
	gmx rmsdist [-f [<.xtc/.trr/...>]] [-s [<.tpr/.gro/...>]] [-n [<.ndx>]]
		    [-equiv [<.dat>]] [-o [<.xvg>]] [-rms [<.xpm>]]
		    [-scl [<.xpm>]] [-mean [<.xpm>]] [-nmr3 [<.xpm>]]
		    [-nmr6 [<.xpm>]] [-noe [<.dat>]] [-b <time>] [-e <time>]
		    [-dt <time>] [-[no]w] [-xvg <enum>] [-nlevels <int>]
		    [-max <real>] [-[no]sumh] [-[no]pbc]

DESCRIPTION
     gmx rmsdist computes the root mean  square  deviation  of	atom  distances,
     which  has  the advantage that no fit is needed like in standard RMS devia-
     tion as computed by gmx rms.  The reference structure  is	taken  from  the
     structure file.  The RMSD at time t is calculated as the RMS of the differ-
     ences  in	distance  between  atom-pairs in the reference structure and the
     structure at time t.

     gmx rmsdist can also produce matrices of the rms distances,  rms  distances
     scaled  with the mean distance and the mean distances and matrices with NMR
     averaged distances (1/r^3 and 1/r^6  averaging).  Finally,  lists	of  atom
     pairs  with  1/r^3  and  1/r^6 averaged distance below the maximum distance
     (-max, which will default to 0.6 in this case) can be generated, by default
     averaging over  equivalent  hydrogens  (all  triplets  of	hydrogens  named
     *[123]).  Additionally a list of equivalent atoms can be supplied (-equiv),
     each line containing a set of equivalent atoms specified as residue  number
     and name and atom name; e.g.:

     HB* 3 SER	HB1 3 SER  HB2

     Residue  and atom names must exactly match those in the structure file, in-
     cluding case. Specifying non-sequential atoms is undefined.

OPTIONS
     Options to specify input files:

     -f [<.xtc/.trr/...>] (traj.xtc)
	    Trajectory: xtc trr cpt gro g96 pdb tng h5md

     -s [<.tpr/.gro/...>] (topol.tpr)
	    Structure+mass(db): tpr gro g96 pdb brk ent

     -n [<.ndx>] (index.ndx) (Optional)
	    Index file

     -equiv [<.dat>] (equiv.dat) (Optional)
	    Generic data file

     Options to specify output files:

     -o [<.xvg>] (distrmsd.xvg)
	    xvgr/xmgr file

     -rms [<.xpm>] (rmsdist.xpm) (Optional)
	    X PixMap compatible matrix file

     -scl [<.xpm>] (rmsscale.xpm) (Optional)
	    X PixMap compatible matrix file

     -mean [<.xpm>] (rmsmean.xpm) (Optional)
	    X PixMap compatible matrix file

     -nmr3 [<.xpm>] (nmr3.xpm) (Optional)
	    X PixMap compatible matrix file

     -nmr6 [<.xpm>] (nmr6.xpm) (Optional)
	    X PixMap compatible matrix file

     -noe [<.dat>] (noe.dat) (Optional)
	    Generic data file

     Other options:

     -b <time> (0)
	    Time of first frame to read from trajectory (default unit ps)

     -e <time> (0)
	    Time of last frame to read from trajectory (default unit ps)

     -dt <time> (0)
	    Only use frame when t MOD dt = first time (default unit ps)

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

     -xvg <enum> (xmgrace)
	    xvg plot formatting: xmgrace, xmgr, none

     -nlevels <int> (40)
	    Discretize RMS in this number of levels

     -max <real> (-1)
	    Maximum level in matrices

     -[no]sumh (yes)
	    Average distance over equivalent hydrogens

     -[no]pbc (yes)
	    Use periodic boundary conditions when computing distances

SEE ALSO
     gmx(1)

     More information about GROMACS is available at <http://www.gromacs.org/>.

COPYRIGHT
     2026, GROMACS development team

2026.3				  Jun 25, 2026			  GMX-RMSDIST(1)

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