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gmx-dielectric(1)               GROMACS Manual               gmx-dielectric(1)

NAME
       gmx-dielectric - Calculate frequency dependent dielectric constants

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

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 and output files:

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

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

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

       -c [<.xvg>] (cole.xvg) (Output)
           xvgr/xmgr file

       Other options:

       -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)

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

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

       -[no]fft  (no)
           use fast fourier transform for correlation function

       -[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, vac, exp5, exp7, exp9,
       erffit

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

SEE ALSO
       gromacs(7)

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

VERSION 5.0.6                                                gmx-dielectric(1)