1 .TH g_energy 1 "Thu 26 Aug 2010" "" "GROMACS suite, VERSION 4.5"
3 g_energy - writes energies to xvg files and displays averages
9 .BI "\-f2" " ener.edr "
10 .BI "\-s" " topol.tpr "
11 .BI "\-o" " energy.xvg "
12 .BI "\-viol" " violaver.xvg "
13 .BI "\-pairs" " pairs.xvg "
14 .BI "\-ora" " orienta.xvg "
15 .BI "\-ort" " orientt.xvg "
16 .BI "\-oda" " orideva.xvg "
17 .BI "\-odr" " oridevr.xvg "
18 .BI "\-odt" " oridevt.xvg "
19 .BI "\-oten" " oriten.xvg "
20 .BI "\-corr" " enecorr.xvg "
21 .BI "\-vis" " visco.xvg "
22 .BI "\-ravg" " runavgdf.xvg "
24 .BI "\-[no]version" ""
31 .BI "\-fetemp" " real "
41 .BI "\-nconstr" " int "
45 .BI "\-acflen" " int "
46 .BI "\-[no]normalize" ""
48 .BI "\-fitfn" " enum "
49 .BI "\-ncskip" " int "
50 .BI "\-beginfit" " real "
51 .BI "\-endfit" " real "
53 \&g_energy extracts energy components or distance restraint
54 \&data from an energy file. The user is prompted to interactively
55 \&select the energy terms she wants.
58 \&Average, RMSD and drift are calculated with full precision from the
59 \&simulation (see printed manual). Drift is calculated by performing
60 \&a LSQ fit of the data to a straight line. The reported total drift
61 \&is the difference of the fit at the first and last point.
62 \&An error estimate of the average is given based on a block averages
63 \&over 5 blocks using the full precision averages. The error estimate
64 \&can be performed over multiple block lengths with the options
65 \&\fB \-nbmin\fR and \fB \-nbmax\fR.
66 \&Note that in most cases the energy files contains averages over all
67 \&MD steps, or over many more points than the number of frames in
68 \&energy file. This makes the g_energy statistics output more accurate
69 \&than the xvg output. When exact averages are not present in the energy
70 \&file the statistics mentioned above is simply over the single, per\-frame
74 \&The term fluctuation gives the RMSD around the LSQ fit.
77 \&Some fluctuation\-dependent properties can be calculated provided
78 \&the correct energy terms are selected. The following properties
81 \&Property Energy terms needed
83 \&\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
85 \&Heat capacity Cp (NPT sims): Enthalpy, Temp
87 \&Heat capacity Cv (NVT sims): Etot, Temp
89 \&Thermal expansion coeff. (NPT): Enthalpy, Vol, Temp
91 \&Isothermal compressibility: Vol, Temp
93 \&Adiabatic bulk modulus: Vol, Temp
95 \&\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
97 \&You always need to set the number of molecules \fB \-nmol\fR, and,
98 \&if you used constraints in your simulations you will need to give
99 \&the number of constraints per molecule \fB \-nconstr\fR in order to
100 \&correct for this: (nconstr/2) kB is subtracted from the heat
101 \&capacity in this case. For instance in the case of rigid water
102 \&you need to give the value 3 to this option.
105 \&When the \fB \-viol\fR option is set, the time averaged
106 \&violations are plotted and the running time\-averaged and
107 \&instantaneous sum of violations are recalculated. Additionally
108 \&running time\-averaged and instantaneous distances between
109 \&selected pairs can be plotted with the \fB \-pairs\fR option.
112 \&Options \fB \-ora\fR, \fB \-ort\fR, \fB \-oda\fR, \fB \-odr\fR and
113 \&\fB \-odt\fR are used for analyzing orientation restraint data.
114 \&The first two options plot the orientation, the last three the
115 \&deviations of the orientations from the experimental values.
116 \&The options that end on an 'a' plot the average over time
117 \&as a function of restraint. The options that end on a 't'
118 \&prompt the user for restraint label numbers and plot the data
119 \&as a function of time. Option \fB \-odr\fR plots the RMS
120 \&deviation as a function of restraint.
121 \&When the run used time or ensemble averaged orientation restraints,
122 \&option \fB \-orinst\fR can be used to analyse the instantaneous,
123 \¬ ensemble\-averaged orientations and deviations instead of
124 \&the time and ensemble averages.
127 \&Option \fB \-oten\fR plots the eigenvalues of the molecular order
128 \&tensor for each orientation restraint experiment. With option
129 \&\fB \-ovec\fR also the eigenvectors are plotted.
132 \&With \fB \-fee\fR an estimate is calculated for the free\-energy
133 \&difference with an ideal gas state:
135 \& Delta A = A(N,V,T) \- A_idgas(N,V,T) = kT ln e(Upot/kT)
137 \& Delta G = G(N,p,T) \- G_idgas(N,p,T) = kT ln e(Upot/kT)
139 \&where k is Boltzmann's constant, T is set by \fB \-fetemp\fR and
140 \&the average is over the ensemble (or time in a trajectory).
141 \&Note that this is in principle
142 \&only correct when averaging over the whole (Boltzmann) ensemble
143 \&and using the potential energy. This also allows for an entropy
146 \& Delta S(N,V,T) = S(N,V,T) \- S_idgas(N,V,T) = (Upot \- Delta A)/T
148 \& Delta S(N,p,T) = S(N,p,T) \- S_idgas(N,p,T) = (Upot + pV \- Delta G)/T
152 \&When a second energy file is specified (\fB \-f2\fR), a free energy
153 \&difference is calculated dF = \-kT ln e \-(EB\-EA)/kT A ,
154 \&where EA and EB are the energies from the first and second energy
155 \&files, and the average is over the ensemble A. \fB NOTE\fR that
156 \&the energies must both be calculated from the same trajectory.
158 .BI "\-f" " ener.edr"
162 .BI "\-f2" " ener.edr"
166 .BI "\-s" " topol.tpr"
168 Run input file: tpr tpb tpa
170 .BI "\-o" " energy.xvg"
174 .BI "\-viol" " violaver.xvg"
178 .BI "\-pairs" " pairs.xvg"
182 .BI "\-ora" " orienta.xvg"
186 .BI "\-ort" " orientt.xvg"
190 .BI "\-oda" " orideva.xvg"
194 .BI "\-odr" " oridevr.xvg"
198 .BI "\-odt" " oridevt.xvg"
202 .BI "\-oten" " oriten.xvg"
206 .BI "\-corr" " enecorr.xvg"
210 .BI "\-vis" " visco.xvg"
214 .BI "\-ravg" " runavgdf.xvg"
220 Print help info and quit
222 .BI "\-[no]version" "no "
223 Print version info and quit
225 .BI "\-nice" " int" " 19"
228 .BI "\-b" " time" " 0 "
229 First frame (ps) to read from trajectory
231 .BI "\-e" " time" " 0 "
232 Last frame (ps) to read from trajectory
235 View output xvg, xpm, eps and pdb files
237 .BI "\-xvg" " enum" " xmgrace"
238 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
240 .BI "\-[no]fee" "no "
241 Do a free energy estimate
243 .BI "\-fetemp" " real" " 300 "
244 Reference temperature for free energy calculation
246 .BI "\-zero" " real" " 0 "
247 Subtract a zero\-point energy
249 .BI "\-[no]sum" "no "
250 Sum the energy terms selected rather than display them all
253 Print energies in high precision
255 .BI "\-nbmin" " int" " 5"
256 Minimum number of blocks for error estimate
258 .BI "\-nbmax" " int" " 5"
259 Maximum number of blocks for error estimate
261 .BI "\-[no]mutot" "no "
262 Compute the total dipole moment from the components
264 .BI "\-skip" " int" " 0"
265 Skip number of frames between data points
267 .BI "\-[no]aver" "no "
268 Also print the exact average and rmsd stored in the energy frames (only when 1 term is requested)
270 .BI "\-nmol" " int" " 1"
271 Number of molecules in your sample: the energies are divided by this number
273 .BI "\-nconstr" " int" " 0"
274 Number of constraints per molecule. Necessary for calculating the heat capacity
276 .BI "\-[no]fluc" "no "
277 Calculate autocorrelation of energy fluctuations rather than energy itself
279 .BI "\-[no]orinst" "no "
280 Analyse instantaneous orientation data
282 .BI "\-[no]ovec" "no "
283 Also plot the eigenvectors with \-oten
285 .BI "\-acflen" " int" " \-1"
286 Length of the ACF, default is half the number of frames
288 .BI "\-[no]normalize" "yes "
291 .BI "\-P" " enum" " 0"
292 Order of Legendre polynomial for ACF (0 indicates none): \fB 0\fR, \fB 1\fR, \fB 2\fR or \fB 3\fR
294 .BI "\-fitfn" " enum" " none"
295 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
297 .BI "\-ncskip" " int" " 0"
298 Skip N points in the output file of correlation functions
300 .BI "\-beginfit" " real" " 0 "
301 Time where to begin the exponential fit of the correlation function
303 .BI "\-endfit" " real" " \-1 "
304 Time where to end the exponential fit of the correlation function, \-1 is until the end
309 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.