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GMX-PRINCIPAL(1)		    GROMACS		      GMX-PRINCIPAL(1)

NAME
       gmx-principal  -	 Calculate  principal  axes  of	inertia	for a group of
       atoms

SYNOPSIS
	  gmx principal	[-f [<.xtc/.trr/...>]] [-s [<.tpr/.gro/...>]]
		       [-n [<.ndx>]] [-a1 [<.xvg>]] [-a2 [<.xvg>]]
		       [-a3 [<.xvg>]] [-om [<.xvg>]] [-b <time>] [-e <time>]
		       [-dt <time>] [-tu <enum>] [-[no]w] [-xvg	<enum>]
		       [-[no]foo]

DESCRIPTION
       gmx principal calculates	the three principal  axes  of  inertia	for  a
       group  of atoms.	NOTE: Old versions of GROMACS wrote the	output data in
       a strange transposed way. As of GROMACS 5.0, the	output file paxis1.dat
       contains	the x/y/z components of	the first (major) principal  axis  for
       each  frame,  and similarly for the middle and minor axes in paxis2.dat
       and paxis3.dat.

OPTIONS
       Options to specify input	files:

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

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

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

       Options to specify output files:

       -a1 [<.xvg>] (paxis1.xvg)
	      xvgr/xmgr	file

       -a2 [<.xvg>] (paxis2.xvg)
	      xvgr/xmgr	file

       -a3 [<.xvg>] (paxis3.xvg)
	      xvgr/xmgr	file

       -om [<.xvg>] (moi.xvg)
	      xvgr/xmgr	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)

       -tu <enum> (ps)
	      Unit for time values: fs,	ps, ns,	us, ms,	s

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

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

       -[no]foo	(no)
	      Dummy option to avoid empty array

SEE ALSO
       gmx(1)

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

COPYRIGHT
       2025, GROMACS development team

2025.0				 Feb 10, 2025		      GMX-PRINCIPAL(1)

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