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       g_dielectric - calculates frequency dependent dielectric constants

       VERSION 4.0.1


       g_dielectric -f dipcorr.xvg -d deriv.xvg -o epsw.xvg -c cole.xvg -[no]h
       -nice int -b time -e time -dt time -[no]w  -[no]xvgr  -[no]fft  -[no]x1
       -eint  real  -bfit  real -efit real -tail real -A real -tau1 real -tau2
       real -eps0 real -epsRF real -fix int -ffn enum -nsmooth int


       dielectric calculates frequency dependent dielectric constants from the
       autocorrelation function of the total dipole moment in your simulation.
       This ACF can be generated by g_dipoles.  For an estimate of  the  error
       you  can run g_statistics on the ACF, and use the output thus generated
       for this program.  The functional forms of the available functions are:

       One  parmeter  : y = Exp[-a1 x] Two parmeters : y = a2 Exp[-a1 x] Three
       parmeter: y = a2 Exp[-a1 x] + (1 - a2) Exp[-a3 x] Startvalues  for  the
       fit  procedure can be given on the commandline.  It is also possible to
       fix parameters at their start value, use -fix with the  number  of  the
       parameter you want to fix.

       Three  output  files  are  generated,  the  first  contains the ACF, an
       exponential fit to it with 1, 2 or  3  parameters,  and  the  numerical
       derivative  of  the combination data/fit.  The second file contains the
       real  and  imaginary  parts  of  the   frequency-dependent   dielectric
       constant,  the  last gives a plot known as the Cole-Cole plot, in which
       the   imaginary  component  is  plotted  as  a  function  of  the  real
       component.   For  a  pure exponential relaxation (Debye relaxation) the
       latter plot should be one half of a circle


       -f dipcorr.xvg Input
        xvgr/xmgr file

       -d deriv.xvg Output
        xvgr/xmgr file

       -o epsw.xvg Output
        xvgr/xmgr file

       -c cole.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

        use fast fourier transform for correlation function

        use first column as X axis rather than first data set

       -eint real 5
        Time were to end the integration of the data and start to use the fit

       -bfit real 5
        Begin time of fit

       -efit real 500
        End time of fit

       -tail real 500
        Length of function including data and tail from fit

       -A real 0.5
        Start value for fit parameter A

       -tau1 real 10
        Start value for fit parameter tau1

       -tau2 real 1
        Start value for fit parameter tau2

       -eps0 real 80
        Epsilon 0 of your liquid

       -epsRF real 78.5
        Epsilon  of  the  reaction field used in your simulation. A value of 0
       means infinity.

       -fix int 0
        Fix parameters at their start values, A (2), tau1 (1), or tau2 (4)

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

       -nsmooth int 3
        Number of points for smoothing



       More      information     about     GROMACS     is     available     at

                                Thu 16 Oct 2008                g_dielectric(1)