g_dielectric(1)

1g_dielectric(1)           GROMACS suite, VERSION 4.5           g_dielectric(1)
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NAME

6       g_dielectric - calculates frequency dependent dielectric constants
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8       VERSION 4.5
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SYNOPSIS

11       g_dielectric -f dipcorr.xvg -d deriv.xvg -o epsw.xvg -c cole.xvg -[no]h
12       -[no]version -nice int -b time  -e  time  -dt  time  -[no]w  -xvg  enum
13       -[no]fft  -[no]x1  -eint  real -bfit real -efit real -tail real -A real
14       -tau1 real -tau2 real  -eps0  real  -epsRF  real  -fix  int  -ffn  enum
15       -nsmooth int
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DESCRIPTION

18       dielectric calculates frequency dependent dielectric constants from the
19       autocorrelation function of the total dipole moment in your simulation.
20       This  ACF  can be generated by g_dipoles.  For an estimate of the error
21       you can run g_statistics on the ACF, and use the output thus  generated
22       for this program.  The functional forms of the available functions are:
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25       One  parameter   :  y = Exp[-a1 x], Two parameters : y = a2 Exp[-a1 x],
26       Three parameters: y = a2 Exp[-a1 x] + (1 - a2) Exp[-a3 x].  Start  val‐
27       ues for the fit procedure can be given on the command line.  It is also
28       possible to fix parameters at their start value, use -fix with the num‐
29       ber of the parameter you want to fix.
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32       Three  output files are generated, the first contains the ACF, an expo‐
33       nential fit to it with 1, 2 or 3 parameters, and the numerical  deriva‐
34       tive  of  the  combination data/fit.  The second file contains the real
35       and imaginary parts of the frequency-dependent dielectric constant, the
36       last  gives  a plot known as the Cole-Cole plot, in which the imaginary
37       component is plotted as a function of the real component.  For  a  pure
38       exponential relaxation (Debye relaxation) the latter plot should be one
39       half of a circle.
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FILES

42       -f dipcorr.xvg Input
43        xvgr/xmgr file
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45       -d deriv.xvg Output
46        xvgr/xmgr file
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48       -o epsw.xvg Output
49        xvgr/xmgr file
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51       -c cole.xvg Output
52        xvgr/xmgr file
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OTHER OPTIONS

56       -[no]hno
57        Print help info and quit
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59       -[no]versionno
60        Print version info and quit
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62       -nice int 19
63        Set the nicelevel
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65       -b time 0
66        First frame (ps) to read from trajectory
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68       -e time 0
69        Last frame (ps) to read from trajectory
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71       -dt time 0
72        Only use frame when t MOD dt = first time (ps)
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74       -[no]wno
75        View output xvg, xpm, eps and pdb files
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77       -xvg enum xmgrace
78        xvg plot formatting:  xmgrace,  xmgr or  none
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80       -[no]fftno
81        use fast fourier transform for correlation function
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83       -[no]x1yes
84        use first column as X axis rather than first data set
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86       -eint real 5
87        Time were to end the integration of the data and start to use the fit
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89       -bfit real 5
90        Begin time of fit
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92       -efit real 500
93        End time of fit
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95       -tail real 500
96        Length of function including data and tail from fit
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98       -A real 0.5
99        Start value for fit parameter A
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101       -tau1 real 10
102        Start value for fit parameter tau1
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104       -tau2 real 1
105        Start value for fit parameter tau2
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107       -eps0 real 80
108        Epsilon 0 of your liquid
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110       -epsRF real 78.5
111        Epsilon of the reaction field used in your simulation. A  value  of  0
112       means infinity.
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114       -fix int 0
115        Fix parameters at their start values, A (2), tau1 (1), or tau2 (4)
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117       -ffn enum none
118        Fit  function:   none,   exp,   aexp,   exp_exp,  vac,  exp5,  exp7 or
119       exp9
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121       -nsmooth int 3
122        Number of points for smoothing
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NAME

SYNOPSIS

DESCRIPTION

FILES

OTHER OPTIONS

SEE ALSO