1 .TH g_rotacf 1 "Thu 26 Aug 2010" "" "GROMACS suite, VERSION 4.5"
3 g_rotacf - calculates the rotational correlation function for molecules
9 .BI "\-s" " topol.tpr "
10 .BI "\-n" " index.ndx "
11 .BI "\-o" " rotacf.xvg "
13 .BI "\-[no]version" ""
22 .BI "\-acflen" " int "
23 .BI "\-[no]normalize" ""
25 .BI "\-fitfn" " enum "
26 .BI "\-ncskip" " int "
27 .BI "\-beginfit" " real "
28 .BI "\-endfit" " real "
30 \&g_rotacf calculates the rotational correlation function
31 \&for molecules. Three atoms (i,j,k) must be given in the index
32 \&file, defining two vectors ij and jk. The rotational acf
33 \&is calculated as the autocorrelation function of the vector
34 \&n = ij x jk, i.e. the cross product of the two vectors.
35 \&Since three atoms span a plane, the order of the three atoms
36 \&does not matter. Optionally, controlled by the \-d switch, you can
37 \&calculate the rotational correlation function for linear molecules
38 \&by specifying two atoms (i,j) in the index file.
45 \&g_rotacf \-P 1 \-nparm 2 \-fft \-n index \-o rotacf\-x\-P1
46 \&\-fa expfit\-x\-P1 \-beginfit 2.5 \-endfit 20.0
49 \&This will calculate the rotational correlation function using a first
50 \&order Legendre polynomial of the angle of a vector defined by the index
51 \&file. The correlation function will be fitted from 2.5 ps till 20.0 ps
52 \&to a two parameter exponential.
57 Trajectory: xtc trr trj gro g96 pdb cpt
59 .BI "\-s" " topol.tpr"
61 Run input file: tpr tpb tpa
63 .BI "\-n" " index.ndx"
67 .BI "\-o" " rotacf.xvg"
73 Print help info and quit
75 .BI "\-[no]version" "no "
76 Print version info and quit
78 .BI "\-nice" " int" " 19"
81 .BI "\-b" " time" " 0 "
82 First frame (ps) to read from trajectory
84 .BI "\-e" " time" " 0 "
85 Last frame (ps) to read from trajectory
87 .BI "\-dt" " time" " 0 "
88 Only use frame when t MOD dt = first time (ps)
91 View output xvg, xpm, eps and pdb files
93 .BI "\-xvg" " enum" " xmgrace"
94 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
97 Use index doublets (vectors) for correlation function instead of triplets (planes)
99 .BI "\-[no]aver" "yes "
100 Average over molecules
102 .BI "\-acflen" " int" " \-1"
103 Length of the ACF, default is half the number of frames
105 .BI "\-[no]normalize" "yes "
108 .BI "\-P" " enum" " 0"
109 Order of Legendre polynomial for ACF (0 indicates none): \fB 0\fR, \fB 1\fR, \fB 2\fR or \fB 3\fR
111 .BI "\-fitfn" " enum" " none"
112 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
114 .BI "\-ncskip" " int" " 0"
115 Skip N points in the output file of correlation functions
117 .BI "\-beginfit" " real" " 0 "
118 Time where to begin the exponential fit of the correlation function
120 .BI "\-endfit" " real" " \-1 "
121 Time where to end the exponential fit of the correlation function, \-1 is until the end
126 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.