NAME

       gmx-dielectric - Calculate frequency dependent dielectric constants

SYNOPSIS

          gmx dielectric [-f [<.xvg>]] [-d [<.xvg>]] [-o [<.xvg>]] [-c [<.xvg>]]
                       [-b <time>] [-e <time>] [-dt <time>] [-[no]w]
                       [-xvg <enum>] [-[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>]

DESCRIPTION

       gmx  dielectric  calculates frequency dependent dielectric constants from the autocorrelation function of
       the total dipole moment in your simulation. This ACF can be generated by  gmx  dipoles.   The  functional
       forms of the available functions are:

          • One parameter:    y = exp(-a_1 x),

          • Two parameters:   y = a_2 exp(-a_1 x),

          • Three parameters: y = a_2 exp(-a_1 x) + (1 - a_2) exp(-a_3 x).

       Start  values  for  the  fit  procedure  can  be  given  on the command line.  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.

OPTIONS

       Options to specify input files:

       -f [<.xvg>] (dipcorr.xvg)
              xvgr/xmgr file

       Options to specify output files:

       -d [<.xvg>] (deriv.xvg)
              xvgr/xmgr file

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

       -c [<.xvg>] (cole.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)

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

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

       -[no]x1 (yes)
              use first column as x-axis rather than first data set

       -eint <real> (5)
              Time 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)
              epsilon0 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, exp5, exp7, exp9

       -nsmooth <int> (3)
              Number of points for smoothing

SEE ALSO

       gmx(1)

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

COPYRIGHT

       2020, GROMACS development team