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       g_density - calculates the density of the system

       VERSION 4.0.1


       g_density  -f  traj.xtc  -n index.ndx -s topol.tpr -ei electrons.dat -o
       density.xvg -[no]h -nice int -b time -e time -dt time -[no]w  -[no]xvgr
       -d string -sl int -dens enum -ng int -[no]symm -[no]center


       Compute  partial  densities  across  the  box,  using  an  index  file.
       Densities in kg/m3, number  densities  or  electron  densities  can  be
       calculated.  For  electron  densities,  a file describing the number of
       electrons for each type of atom should  be  provided  using   -ei.   It
       should look like:


          atomname = nrelectrons

          atomname = nrelectrons

       The  first  line  contains  the  number of lines to read from the file.
       There should be one line for each unique atom name in your system.  The
       number  of  electrons  for  each atom is modified by its atomic partial


       -f traj.xtc Input
        Trajectory: xtc trr trj gro g96 pdb cpt

       -n index.ndx Input, Opt.
        Index file

       -s topol.tpr Input
        Run input file: tpr tpb tpa

       -ei electrons.dat Input, Opt.
        Generic data file

       -o density.xvg Output
        xvgr/xmgr file


        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)

        View output xvg, xpm, eps and pdb files

        Add specific codes (legends etc.) in the  output  xvg  files  for  the
       xmgrace program

       -d string Z
        Take the normal on the membrane in direction X, Y or Z.

       -sl int 50
        Divide the box in nr slices.

       -dens enum mass
        Density:  mass,  number,  charge or  electron

       -ng int 1
        Number of groups to compute densities of

        Symmetrize  the  density  along  the axis, with respect to the center.
       Useful for bilayers.

        Shift the center of mass along the axis to zero. This  means  if  your
       axis  is  Z  and  your box is bX, bY, bZ, the center of mass will be at
       bX/2, bY/2, 0.


       - When calculating electron densities, atomnames are  used  instead  of
       types. This is bad.



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                                Thu 16 Oct 2008                   g_density(1)