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

6       g_velacc - calculates velocity autocorrelation functions
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8       VERSION 4.5
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SYNOPSIS

11       g_velacc  -f  traj.trr  -s  topol.tpr  -n  index.ndx  -o vac.xvg -[no]h
12       -[no]version -nice int -b time -e time -dt time -[no]w -xvg enum -[no]m
13       -[no]mol  -acflen  int  -[no]normalize  -P enum -fitfn enum -ncskip int
14       -beginfit real -endfit real
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DESCRIPTION

17       g_velacc computes the velocity autocorrelation function.  When the   -m
18       option is used, the momentum autocorrelation function is calculated.
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21       With option  -mol the velocity autocorrelation function of molecules is
22       calculated. In this case the index group  should  consist  of  molecule
23       numbers instead of atom numbers.
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FILES

26       -f traj.trr Input
27        Full precision trajectory: trr trj cpt
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29       -s topol.tpr Input, Opt.
30        Structure+mass(db): tpr tpb tpa gro g96 pdb
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32       -n index.ndx Input, Opt.
33        Index file
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35       -o vac.xvg Output
36        xvgr/xmgr file
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OTHER OPTIONS

40       -[no]hno
41        Print help info and quit
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43       -[no]versionno
44        Print version info and quit
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46       -nice int 19
47        Set the nicelevel
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49       -b time 0
50        First frame (ps) to read from trajectory
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52       -e time 0
53        Last frame (ps) to read from trajectory
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55       -dt time 0
56        Only use frame when t MOD dt = first time (ps)
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58       -[no]wno
59        View output xvg, xpm, eps and pdb files
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61       -xvg enum xmgrace
62        xvg plot formatting:  xmgrace,  xmgr or  none
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64       -[no]mno
65        Calculate the momentum autocorrelation function
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67       -[no]molno
68        Calculate the velocity acf of molecules
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70       -acflen int -1
71        Length of the ACF, default is half the number of frames
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73       -[no]normalizeyes
74        Normalize ACF
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76       -P enum 0
77        Order of Legendre polynomial for ACF (0 indicates none):  0,  1,  2 or
78       3
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80       -fitfn enum none
81        Fit function:  none,  exp,  aexp,   exp_exp,   vac,   exp5,   exp7  or
82       exp9
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84       -ncskip int 0
85        Skip N points in the output file of correlation functions
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87       -beginfit real 0
88        Time where to begin the exponential fit of the correlation function
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90       -endfit real -1
91        Time  where to end the exponential fit of the correlation function, -1
92       is until the end
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SEE ALSO

96       gromacs(7)
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98       More  information  about  GROMACS  is  available  at   <http://www.gro‐
99       macs.org/>.
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103                                Thu 26 Aug 2010                    g_velacc(1)
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