NAME¶

gmx-sham - Compute free energies or other histograms from histograms

SYNOPSIS¶

gmx sham [-f [<.xvg>]] [-ge [<.xvg>]] [-ene [<.xvg>]]
[-dist [<.xvg>]] [-histo [<.xvg>]] [-bin [<.ndx>]]
[-lp [<.xpm>]] [-ls [<.xpm>]] [-lsh [<.xpm>]]
[-lss [<.xpm>]] [-ls3 [<.pdb>]] [-g [<.log>]] [-nice <int>]
[-[no]w] [-xvg <enum>] [-[no]time] [-b <real>] [-e <real>]
[-ttol <real>] [-n <int>] [-[no]d] [-[no]sham]
[-tsham <real>] [-pmin <real>] [-dim <vector>]
[-ngrid <vector>] [-xmin <vector>] [-xmax <vector>]
[-pmax <real>] [-gmax <real>] [-emin <real>] [-emax <real>]
[-nlevels <int>]

DESCRIPTION¶

gmx sham makes multi-dimensional free-energy, enthalpy and entropy plots. gmx sham reads one or more .xvg files and analyzes data sets. The basic purpose of gmx sham is to plot Gibbs free energy landscapes (option -ls) by Bolzmann inverting multi-dimensional histograms (option -lp), but it can also make enthalpy (option -lsh) and entropy (option -lss) plots. The histograms can be made for any quantities the user supplies. A line in the input file may start with a time (see option -time) and any number of y-values may follow. Multiple sets can also be read when they are separated by & (option -n), in this case only one y-value is read from each line. All lines starting with and @ are skipped. Option -ge can be used to supply a file with free energies when the ensemble is not a Boltzmann ensemble, but needs to be biased by this free energy. One free energy value is required for each (multi-dimensional) data point in the -f input. Option -ene can be used to supply a file with energies. These energies are used as a weighting function in the single histogram analysis method by Kumar et al. When temperatures are supplied (as a second column in the file), an experimental weighting scheme is applied. In addition the vales are used for making enthalpy and entropy plots. With option -dim, dimensions can be gives for distances. When a distance is 2- or 3-dimensional, the circumference or surface sampled by two particles increases with increasing distance. Depending on what one would like to show, one can choose to correct the histogram and free-energy for this volume effect. The probability is normalized by r and r2 for dimensions of 2 and 3, respectively. A value of -1 is used to indicate an angle in degrees between two vectors: a sin(angle) normalization will be applied. Note that for angles between vectors the inner-product or cosine is the natural quantity to use, as it will produce bins of the same volume.

OPTIONS¶

Options to specify input and output files: -f [<.xvg>] (graph.xvg) (Input)
xvgr/xmgr file -ge [<.xvg>] (gibbs.xvg) (Input, Optional)
xvgr/xmgr file -ene [<.xvg>] (esham.xvg) (Input, Optional)
xvgr/xmgr file -dist [<.xvg>] (ener.xvg) (Output, Optional)
xvgr/xmgr file -histo [<.xvg>] (edist.xvg) (Output, Optional)
xvgr/xmgr file -bin [<.ndx>] (bindex.ndx) (Output, Optional)
Index file -lp [<.xpm>] (prob.xpm) (Output, Optional)
X PixMap compatible matrix file -ls [<.xpm>] (gibbs.xpm) (Output, Optional)
X PixMap compatible matrix file -lsh [<.xpm>] (enthalpy.xpm) (Output, Optional)
X PixMap compatible matrix file -lss [<.xpm>] (entropy.xpm) (Output, Optional)
X PixMap compatible matrix file -ls3 [<.pdb>] (gibbs3.pdb) (Output, Optional)
Protein data bank file -g [<.log>] (shamlog.log) (Output, Optional)
Log file Other options: -nice <int> (19)
Set the nicelevel -[no]w (no)
View output .xvg, .xpm, .eps and .pdb files -xvg <enum> (xmgrace)
xvg plot formatting: xmgrace, xmgr, none -[no]time (yes)
Expect a time in the input -b <real> (-1)
First time to read from set -e <real> (-1)
Last time to read from set -ttol <real> (0)
Tolerance on time in appropriate units (usually ps) -n <int> (1)
Read this number of sets separated by lines containing only an ampersand -[no]d (no)
Use the derivative -[no]sham (yes)
Turn off energy weighting even if energies are given -tsham <real> (298.15)
Temperature for single histogram analysis -pmin <real> (0)
Minimum probability. Anything lower than this will be set to zero -dim <vector> (1 1 1)
Dimensions for distances, used for volume correction (max 3 values, dimensions 3 will get the same value as the last) -ngrid <vector> (32 32 32)
Number of bins for energy landscapes (max 3 values, dimensions 3 will get the same value as the last) -xmin <vector> (0 0 0)
Minimum for the axes in energy landscape (see above for 3 dimensions) -xmax <vector> (1 1 1)
Maximum for the axes in energy landscape (see above for 3 dimensions) -pmax <real> (0)
Maximum probability in output, default is calculate -gmax <real> (0)
Maximum free energy in output, default is calculate -emin <real> (0)
Minimum enthalpy in output, default is calculate -emax <real> (0)
Maximum enthalpy in output, default is calculate -nlevels <int> (25)
Number of levels for energy landscape

SEE ALSO¶

gromacs(7) More information about GROMACS is available at <http://www.gromacs.org/>.