1 .TH g_energy 1 "Fri 19 Apr 2013" "" "GROMACS suite, VERSION 4.5.7"
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 "
23 .BI "\-odh" " dhdl.xvg "
25 .BI "\-[no]version" ""
32 .BI "\-fetemp" " real "
42 .BI "\-[no]fluct_props" ""
43 .BI "\-[no]driftcorr" ""
47 .BI "\-acflen" " int "
48 .BI "\-[no]normalize" ""
50 .BI "\-fitfn" " enum "
51 .BI "\-ncskip" " int "
52 .BI "\-beginfit" " real "
53 .BI "\-endfit" " real "
55 \&\fB g_energy\fR extracts energy components or distance restraint
56 \&data from an energy file. The user is prompted to interactively
57 \&select the desired energy terms.
60 \&Average, RMSD, and drift are calculated with full precision from the
61 \&simulation (see printed manual). Drift is calculated by performing
62 \&a least\-squares fit of the data to a straight line. The reported total drift
63 \&is the difference of the fit at the first and last point.
64 \&An error estimate of the average is given based on a block averages
65 \&over 5 blocks using the full\-precision averages. The error estimate
66 \&can be performed over multiple block lengths with the options
67 \&\fB \-nbmin\fR and \fB \-nbmax\fR.
68 \&\fB Note\fR that in most cases the energy files contains averages over all
69 \&MD steps, or over many more points than the number of frames in
70 \&energy file. This makes the \fB g_energy\fR statistics output more accurate
71 \&than the \fB .xvg\fR output. When exact averages are not present in the energy
72 \&file, the statistics mentioned above are simply over the single, per\-frame
76 \&The term fluctuation gives the RMSD around the least\-squares fit.
79 \&Some fluctuation\-dependent properties can be calculated provided
80 \&the correct energy terms are selected, and that the command line option
81 \&\fB \-fluct_props\fR is given. The following properties
84 \&Property Energy terms needed
86 \&\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
88 \&Heat capacity C_p (NPT sims): Enthalpy, Temp
90 \&Heat capacity C_v (NVT sims): Etot, Temp
92 \&Thermal expansion coeff. (NPT): Enthalpy, Vol, Temp
94 \&Isothermal compressibility: Vol, Temp
96 \&Adiabatic bulk modulus: Vol, Temp
98 \&\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
100 \&You always need to set the number of molecules \fB \-nmol\fR.
101 \&The C_p/C_v computations do \fB not\fR include any corrections
102 \&for quantum effects. Use the \fB g_dos\fR program if you need that (and you do).
104 When the \fB \-viol\fR option is set, the time averaged
105 \&violations are plotted and the running time\-averaged and
106 \&instantaneous sum of violations are recalculated. Additionally
107 \&running time\-averaged and instantaneous distances between
108 \&selected pairs can be plotted with the \fB \-pairs\fR option.
111 \&Options \fB \-ora\fR, \fB \-ort\fR, \fB \-oda\fR, \fB \-odr\fR and
112 \&\fB \-odt\fR are used for analyzing orientation restraint data.
113 \&The first two options plot the orientation, the last three the
114 \&deviations of the orientations from the experimental values.
115 \&The options that end on an 'a' plot the average over time
116 \&as a function of restraint. The options that end on a 't'
117 \&prompt the user for restraint label numbers and plot the data
118 \&as a function of time. Option \fB \-odr\fR plots the RMS
119 \&deviation as a function of restraint.
120 \&When the run used time or ensemble averaged orientation restraints,
121 \&option \fB \-orinst\fR can be used to analyse the instantaneous,
122 \¬ ensemble\-averaged orientations and deviations instead of
123 \&the time and ensemble averages.
126 \&Option \fB \-oten\fR plots the eigenvalues of the molecular order
127 \&tensor for each orientation restraint experiment. With option
128 \&\fB \-ovec\fR also the eigenvectors are plotted.
131 \&Option \fB \-odh\fR extracts and plots the free energy data
132 \&(Hamiltoian differences and/or the Hamiltonian derivative dhdl)
133 \&from the \fB ener.edr\fR file.
136 \&With \fB \-fee\fR an estimate is calculated for the free\-energy
137 \&difference with an ideal gas state:
139 \& Delta A = A(N,V,T) \- A_idealgas(N,V,T) = kT ln(exp(U_pot/kT))
141 \& Delta G = G(N,p,T) \- G_idealgas(N,p,T) = kT ln(exp(U_pot/kT))
143 \&where k is Boltzmann's constant, T is set by \fB \-fetemp\fR and
144 \&the average is over the ensemble (or time in a trajectory).
145 \&Note that this is in principle
146 \&only correct when averaging over the whole (Boltzmann) ensemble
147 \&and using the potential energy. This also allows for an entropy
150 \& Delta S(N,V,T) = S(N,V,T) \- S_idealgas(N,V,T) = (U_pot \- Delta A)/T
152 \& Delta S(N,p,T) = S(N,p,T) \- S_idealgas(N,p,T) = (U_pot + pV \- Delta G)/T
156 \&When a second energy file is specified (\fB \-f2\fR), a free energy
157 \&difference is calculated
158 dF = \-kT ln(exp(\-(E_B\-E_A)/kT)_A) ,
159 \&where E_A and E_B are the energies from the first and second energy
160 \&files, and the average is over the ensemble A. The running average
161 \&of the free energy difference is printed to a file specified by \fB \-ravg\fR.
162 \&\fB Note\fR that the energies must both be calculated from the same trajectory.
164 .BI "\-f" " ener.edr"
168 .BI "\-f2" " ener.edr"
172 .BI "\-s" " topol.tpr"
174 Run input file: tpr tpb tpa
176 .BI "\-o" " energy.xvg"
180 .BI "\-viol" " violaver.xvg"
184 .BI "\-pairs" " pairs.xvg"
188 .BI "\-ora" " orienta.xvg"
192 .BI "\-ort" " orientt.xvg"
196 .BI "\-oda" " orideva.xvg"
200 .BI "\-odr" " oridevr.xvg"
204 .BI "\-odt" " oridevt.xvg"
208 .BI "\-oten" " oriten.xvg"
212 .BI "\-corr" " enecorr.xvg"
216 .BI "\-vis" " visco.xvg"
220 .BI "\-ravg" " runavgdf.xvg"
224 .BI "\-odh" " dhdl.xvg"
230 Print help info and quit
232 .BI "\-[no]version" "no "
233 Print version info and quit
235 .BI "\-nice" " int" " 19"
238 .BI "\-b" " time" " 0 "
239 First frame (ps) to read from trajectory
241 .BI "\-e" " time" " 0 "
242 Last frame (ps) to read from trajectory
245 View output \fB .xvg\fR, \fB .xpm\fR, \fB .eps\fR and \fB .pdb\fR files
247 .BI "\-xvg" " enum" " xmgrace"
248 xvg plot formatting: \fB xmgrace\fR, \fB xmgr\fR or \fB none\fR
250 .BI "\-[no]fee" "no "
251 Do a free energy estimate
253 .BI "\-fetemp" " real" " 300 "
254 Reference temperature for free energy calculation
256 .BI "\-zero" " real" " 0 "
257 Subtract a zero\-point energy
259 .BI "\-[no]sum" "no "
260 Sum the energy terms selected rather than display them all
263 Print energies in high precision
265 .BI "\-nbmin" " int" " 5"
266 Minimum number of blocks for error estimate
268 .BI "\-nbmax" " int" " 5"
269 Maximum number of blocks for error estimate
271 .BI "\-[no]mutot" "no "
272 Compute the total dipole moment from the components
274 .BI "\-skip" " int" " 0"
275 Skip number of frames between data points
277 .BI "\-[no]aver" "no "
278 Also print the exact average and rmsd stored in the energy frames (only when 1 term is requested)
280 .BI "\-nmol" " int" " 1"
281 Number of molecules in your sample: the energies are divided by this number
283 .BI "\-[no]fluct_props" "no "
284 Compute properties based on energy fluctuations, like heat capacity
286 .BI "\-[no]driftcorr" "no "
287 Useful only for calculations of fluctuation properties. The drift in the observables will be subtracted before computing the fluctuation properties.
289 .BI "\-[no]fluc" "no "
290 Calculate autocorrelation of energy fluctuations rather than energy itself
292 .BI "\-[no]orinst" "no "
293 Analyse instantaneous orientation data
295 .BI "\-[no]ovec" "no "
296 Also plot the eigenvectors with \fB \-oten\fR
298 .BI "\-acflen" " int" " \-1"
299 Length of the ACF, default is half the number of frames
301 .BI "\-[no]normalize" "yes "
304 .BI "\-P" " enum" " 0"
305 Order of Legendre polynomial for ACF (0 indicates none): \fB 0\fR, \fB 1\fR, \fB 2\fR or \fB 3\fR
307 .BI "\-fitfn" " enum" " none"
308 Fit function: \fB none\fR, \fB exp\fR, \fB aexp\fR, \fB exp_exp\fR, \fB vac\fR, \fB exp5\fR, \fB exp7\fR, \fB exp9\fR or \fB erffit\fR
310 .BI "\-ncskip" " int" " 0"
311 Skip this many points in the output file of correlation functions
313 .BI "\-beginfit" " real" " 0 "
314 Time where to begin the exponential fit of the correlation function
316 .BI "\-endfit" " real" " \-1 "
317 Time where to end the exponential fit of the correlation function, \-1 is until the end
322 More information about \fBGROMACS\fR is available at <\fIhttp://www.gromacs.org/\fR>.