1 .TH g_dielectric 1 "Thu 26 Aug 2010" "" "GROMACS suite, VERSION 4.5"
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 \&dielectric 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 g_dipoles.
38 \&For an estimate of the error you can run g_statistics on the
39 \&ACF, and use the output thus generated for this program.
40 \&The functional forms of the available functions are:
43 \&One parameter : y = Exp[\-a1 x],
44 \&Two parameters : y = a2 Exp[\-a1 x],
45 \&Three parameters: y = a2 Exp[\-a1 x] + (1 \- a2) Exp[\-a3 x].
46 \&Start values for the fit procedure can be given on the command line.
47 \&It is also possible to fix parameters at their start value, use \-fix
48 \&with the number of the parameter you want to fix.
52 \&Three output files are generated, the first contains the ACF,
53 \&an exponential fit to it with 1, 2 or 3 parameters, and the
54 \&numerical derivative of the combination data/fit.
55 \&The second file contains the real and imaginary parts of the
56 \&frequency\-dependent dielectric constant, the last gives a plot
57 \&known as the Cole\-Cole plot, in which the imaginary
58 \&component is plotted as a function of the real component.
59 \&For a pure exponential relaxation (Debye relaxation) the latter
60 \&plot should be one half of a circle.
62 .BI "\-f" " dipcorr.xvg"
66 .BI "\-d" " deriv.xvg"
80 Print help info and quit
82 .BI "\-[no]version" "no "
83 Print version info and quit
85 .BI "\-nice" " int" " 19"
88 .BI "\-b" " time" " 0 "
89 First frame (ps) to read from trajectory
91 .BI "\-e" " time" " 0 "
92 Last frame (ps) to read from trajectory
94 .BI "\-dt" " time" " 0 "
95 Only use frame when t MOD dt = first time (ps)
98 View output xvg, xpm, eps and pdb files
100 .BI "\-xvg" " enum" " xmgrace"
101 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
103 .BI "\-[no]fft" "no "
104 use fast fourier transform for correlation function
106 .BI "\-[no]x1" "yes "
107 use first column as X axis rather than first data set
109 .BI "\-eint" " real" " 5 "
110 Time were to end the integration of the data and start to use the fit
112 .BI "\-bfit" " real" " 5 "
115 .BI "\-efit" " real" " 500 "
118 .BI "\-tail" " real" " 500 "
119 Length of function including data and tail from fit
121 .BI "\-A" " real" " 0.5 "
122 Start value for fit parameter A
124 .BI "\-tau1" " real" " 10 "
125 Start value for fit parameter tau1
127 .BI "\-tau2" " real" " 1 "
128 Start value for fit parameter tau2
130 .BI "\-eps0" " real" " 80 "
131 Epsilon 0 of your liquid
133 .BI "\-epsRF" " real" " 78.5 "
134 Epsilon of the reaction field used in your simulation. A value of 0 means infinity.
136 .BI "\-fix" " int" " 0"
137 Fix parameters at their start values, A (2), tau1 (1), or tau2 (4)
139 .BI "\-ffn" " enum" " none"
140 Fit function: \fB none\fR, \fB exp\fR, \fB aexp\fR, \fB exp_exp\fR, \fB vac\fR, \fB exp5\fR, \fB exp7\fR or \fB exp9\fR
142 .BI "\-nsmooth" " int" " 3"
143 Number of points for smoothing
148 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.