1 .TH g_dielectric 1 "Fri 19 Apr 2013" "" "GROMACS suite, VERSION 4.5.7"
3 g_dielectric - calculates frequency dependent dielectric constants
8 .BI "\-f" " dipcorr.xvg "
9 .BI "\-d" " deriv.xvg "
10 .BI "\-o" " epsw.xvg "
11 .BI "\-c" " cole.xvg "
13 .BI "\-[no]version" ""
30 .BI "\-epsRF" " real "
33 .BI "\-nsmooth" " int "
35 \&\fB g_dielectric\fR calculates frequency dependent dielectric constants
36 \&from the autocorrelation function of the total dipole moment in
37 \&your simulation. This ACF can be generated by \fB g_dipoles\fR.
38 \&The functional forms of the available functions are:
41 \&One parameter: y = exp(\-a_1 x),
43 \&Two parameters: y = a_2 exp(\-a_1 x),
45 \&Three parameters: y = a_2 exp(\-a_1 x) + (1 \- a_2) exp(\-a_3 x).
47 \&Start values for the fit procedure can be given on the command line.
48 \&It is also possible to fix parameters at their start value, use \fB \-fix\fR
49 \&with the number of the parameter you want to fix.
53 \&Three output files are generated, the first contains the ACF,
54 \&an exponential fit to it with 1, 2 or 3 parameters, and the
55 \&numerical derivative of the combination data/fit.
56 \&The second file contains the real and imaginary parts of the
57 \&frequency\-dependent dielectric constant, the last gives a plot
58 \&known as the Cole\-Cole plot, in which the imaginary
59 \&component is plotted as a function of the real component.
60 \&For a pure exponential relaxation (Debye relaxation) the latter
61 \&plot should be one half of a circle.
63 .BI "\-f" " dipcorr.xvg"
67 .BI "\-d" " deriv.xvg"
81 Print help info and quit
83 .BI "\-[no]version" "no "
84 Print version info and quit
86 .BI "\-nice" " int" " 19"
89 .BI "\-b" " time" " 0 "
90 First frame (ps) to read from trajectory
92 .BI "\-e" " time" " 0 "
93 Last frame (ps) to read from trajectory
95 .BI "\-dt" " time" " 0 "
96 Only use frame when t MOD dt = first time (ps)
99 View output \fB .xvg\fR, \fB .xpm\fR, \fB .eps\fR and \fB .pdb\fR files
101 .BI "\-xvg" " enum" " xmgrace"
102 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
104 .BI "\-[no]fft" "no "
105 use fast fourier transform for correlation function
107 .BI "\-[no]x1" "yes "
108 use first column as \fI x\fR\-axis rather than first data set
110 .BI "\-eint" " real" " 5 "
111 Time to end the integration of the data and start to use the fit
113 .BI "\-bfit" " real" " 5 "
116 .BI "\-efit" " real" " 500 "
119 .BI "\-tail" " real" " 500 "
120 Length of function including data and tail from fit
122 .BI "\-A" " real" " 0.5 "
123 Start value for fit parameter A
125 .BI "\-tau1" " real" " 10 "
126 Start value for fit parameter tau1
128 .BI "\-tau2" " real" " 1 "
129 Start value for fit parameter tau2
131 .BI "\-eps0" " real" " 80 "
132 epsilon0 of your liquid
134 .BI "\-epsRF" " real" " 78.5 "
135 epsilon of the reaction field used in your simulation. A value of 0 means infinity.
137 .BI "\-fix" " int" " 0"
138 Fix parameters at their start values, A (2), tau1 (1), or tau2 (4)
140 .BI "\-ffn" " enum" " none"
141 Fit function: \fB none\fR, \fB exp\fR, \fB aexp\fR, \fB exp_exp\fR, \fB vac\fR, \fB exp5\fR, \fB exp7\fR, \fB exp9\fR or \fB erffit\fR
143 .BI "\-nsmooth" " int" " 3"
144 Number of points for smoothing
149 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.