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g_dielectric - calculates frequency dependent dielectric constantsVERSION4.0.1

g_dielectric-fdipcorr.xvg-dderiv.xvg-oepsw.xvg-ccole.xvg-[no]h-niceint-btime-etime-dttime-[no]w-[no]xvgr-[no]fft-[no]x1-eintreal-bfitreal-efitreal-tailreal-Areal-tau1real-tau2real-eps0real-epsRFreal-fixint-ffnenum-nsmoothint

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

-fdipcorr.xvgInputxvgr/xmgr file-dderiv.xvgOutputxvgr/xmgr file-oepsw.xvgOutputxvgr/xmgr file-ccole.xvgOutputxvgr/xmgr file

-[no]hnoPrint help info and quit-niceint19Set the nicelevel-btime0First frame (ps) to read from trajectory-etime0Last frame (ps) to read from trajectory-dttime0Only use frame when t MOD dt = first time (ps)-[no]wnoView output xvg, xpm, eps and pdb files-[no]xvgryesAdd specific codes (legends etc.) in the output xvg files for the xmgrace program-[no]fftnouse fast fourier transform for correlation function-[no]x1yesuse first column as X axis rather than first data set-eintreal5Time were to end the integration of the data and start to use the fit-bfitreal5Begin time of fit-efitreal500End time of fit-tailreal500Length of function including data and tail from fit-Areal0.5Start value for fit parameter A-tau1real10Start value for fit parameter tau1-tau2real1Start value for fit parameter tau2-eps0real80Epsilon 0 of your liquid-epsRFreal78.5Epsilon of the reaction field used in your simulation. A value of 0 means infinity.-fixint0Fix parameters at their start values, A (2), tau1 (1), or tau2 (4)-ffnenumnoneFit function:none,exp,aexp,exp_exp,vac,exp5,exp7orexp9-nsmoothint3Number of points for smoothing

gromacs(7)More information aboutGROMACSis available at <http://www.gromacs.org/>. Thu 16 Oct 2008 g_dielectric(1)