g_dielectric(1) - Linux man page
Name
g_dielectric - calculates frequency dependent dielectric constantsVERSION 4.5.4-dev-20110404-bc5695c
Synopsis
Description
g_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 parameter: y = Exp[-a1 x],
Two parameters: y = a2 Exp[-a1 x],
Three parameters: y = a2 Exp[-a1 x] + (1 - a2) Exp[-a3 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.
Files
-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
Other Options
-[no]hno Print help info and quit-[no]versionno Print version 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)
-[no]wno View output .xvg, .xpm, .eps and .pdb files
-xvg enum xmgrace xvg plot formatting: xmgrace, xmgr or none
-[no]fftno use fast fourier transform for correlation function
-[no]x1yes 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 or erffit
-nsmooth int 3 Number of points for smoothing
See Also
gromacs(7)More information about GROMACS is available at <http://www.gromacs.org/>.