[gmx-developers] pressure calculation in GROMACS CVS

David van der Spoel spoel at xray.bmc.uu.se
Wed May 14 22:57:20 CEST 2008


mzink at gwdg.de wrote:
> Hi Berk,
> 
> here are the results from my complete simulation system. The simulations
> were performed with CVS version from 2007-04-07. When preprocessing with
> this version, the pressure is much too low and the volume changes
> significantly during pressure scaling, resulting in a compression of my
> protein (gyration radius declines by 0.2nm in the first steps, berendsen
> tau_p=1ps):
> 
>     Time(ps)  Volume
>     0.000000  33352.519531
>     1.000000  32016.798828
>     2.000000  31509.839844
>     3.000000  31247.882812
>     4.000000  31129.593750
>     5.000000  31069.384766
> 
>     Time(ps)   Pressure
>     0.000000  -1977.399414
>     1.000000  -507.769196
>     2.000000  -282.439423
>     3.000000  -90.428642
>     4.000000  -78.975014
>     5.000000  -46.453594
> 
> When I did grompp with the cvs version from 2007-06-21 or gromacs-331, the
> pressure was about less then 100bar at step 0 and the box volume did not
> change.
So did you run, as Berk suggested, gmxcheck -s1 top33.tpr -s2 top40.tpr 
and look for differences?



> 
> Although the starting structure are identical, mdrun is always the same
> and I checked tpr files with gmxcheck and gmxdump, I cannot find the
> mistake. At the moment I have to perform the simulations with constant
> volume or with cvs versions BEFORE july 2007, otherwise the box
> compression destroys my system. Otherwise I have to run grompp with older
> versions, than it is working with current cvs-mdrun. For me it seems so
> that grompp is the problem and not mdrun but I don't have a clue what's
> going on. Maybe you have an idea?
> 
> Regards,
> Mareike
> 
> 
>> Hi,
>>
>> The results you posted show, according to me, no significant difference
>> in pressure and volume,
>> except for the pressure at step 0.
>>
>> I assume, but you did not state this clearly, that both runs were done
>> with exactly the same
>> mdrun binary. I changed something with the constraining of the initial
>> velocities in mdrun
>> some time ago, which could explain the pressure difference at step 0.
>> If it is really only a grompp version difference and not mdrun, I do not
>> understand how this
>> is possible.
>>
>> You can compare tpr files with:
>> gmxcheck -s1 ... -s2 ...
>>
>> Berk.
>>
>>
>> Mareike Zink wrote:
>>> Dear GROMACS developers,
>>>
>>> I may found a bug in the pressure calculation of the current GROMACS CVS
>>> version:
>>>
>>> My system (protein in water, approx. 320,000 particles) is equilibrated
>>> in an
>>> NPT ensemble and I want to run it with CVS version from 2007-07-04 or
>>> the
>>> current version from 2008-04-15 with a constant pressure of 1bar. The
>>> following pressure and box volumes are given as an output:
>>>
>>>     Time(ps)    Pressure(bar)
>>>     0.000000  1519.933594
>>>     0.200000    1.404368
>>>     0.400000   53.713745
>>>     0.600000  -16.645607
>>>     0.800000  -40.373356
>>>     1.000000   64.932564
>>>
>>>     Time(ps)   Volume(nm³)
>>>     0.000000  2458.407227
>>>     0.200000  2458.920166
>>>     0.400000  2458.617188
>>>     0.600000  2459.025146
>>>     0.800000  2459.828613
>>>     1.000000  2459.592285
>>>
>>> When I did the preprocessing with a CVS version from 2007-06-21 or
>>> GROMACS-3.3.1 but run the simulation with the CVS version from
>>> 2007-07-04 or
>>> 2008-04-15, the pressure and volume look much different:
>>>
>>>     Time(ps)   Pressure(bar)
>>>     0.000000   95.616234
>>>     0.200000    4.654475
>>>     0.400000   59.303020
>>>     0.600000   -7.656351
>>>     0.800000   -1.787814
>>>     1.000000   -9.527036
>>>
>>>     Time(ps)   Volume
>>>     0.000000  2458.407227
>>>     0.200000  2458.871582
>>>     0.400000  2458.587158
>>>     0.600000  2458.832031
>>>     0.800000  2459.606445
>>>     1.000000  2459.485107
>>>
>>>
>>> Maybe there is a problem with the preprocessor. The problem with the
>>> much too
>>> high pressure only occures if grompp was done with a CVS version from
>>> 2007-07-04 or later.
>>>
>>> Furthermore, the system I was using here, is just a subsystem of my
>>> complete
>>> simulation system which contains 4,5 Million atoms. Here I have the same
>>> problem but the pressure is much too small (-2000bar). Due to the wrong
>>> pressure, the pressure coupling rescales the box size within 1ps (my
>>> tau_p)
>>> and compresses the box to a much too small volume. Maybe the pressure
>>> calculation is buggy?
>>> Do you kno anything about this problem?
>>>
>>> My mdp-files for grompp with gromacs331 and cvs are below.
>>>
>>> If you need more information or files, please contact me.
>>>
>>> Thanx,
>>>
>>> Mareike
>>>
>>>
>>> GROMACS 331:
>>>
>>> ;
>>> ;	File 'mdout.mdp' was generated
>>> ;	By user: mzink (37571)
>>> ;	On host: beany
>>> ;	At date: Mon Dec 18 12:45:54 2006
>>> ;
>>>
>>> ; VARIOUS PREPROCESSING OPTIONS
>>> title                    =
>>> ; Preprocessor - specify a full path if necessary.
>>> cpp                      = /lib/cpp
>>> include                  =
>>> define                   =
>>>
>>> ; RUN CONTROL PARAMETERS
>>> integrator               = md
>>> ; Start time and timestep in ps
>>> tinit                    = 0
>>> dt                       = 0.002
>>> nsteps                   = 5000
>>> ; For exact run continuation or redoing part of a run
>>> init_step                = 0
>>> ; mode for center of mass motion removal
>>> comm-mode                = Linear
>>> ; number of steps for center of mass motion removal
>>> nstcomm                  = 1
>>> ; group(s) for center of mass motion removal
>>> comm-grps                =
>>>
>>> ; LANGEVIN DYNAMICS OPTIONS
>>> ; Friction coefficient (amu/ps) and random seed
>>> bd-fric                  = 0
>>> ld_seed                  = 1993
>>>
>>> ; ENERGY MINIMIZATION OPTIONS
>>> ; Force tolerance and initial step-size
>>> emtol                    = 0.000001
>>> emstep                   = 0.01
>>> ; Max number of iterations in relax_shells
>>> niter                    = 100
>>> ; Step size (ps^2) for minimization of flexible constraints
>>> fcstep                   = 0
>>> ; Frequency of steepest descents steps when doing CG
>>> nstcgsteep               = 1000
>>> nbfgscorr                = 10
>>>
>>> ; OUTPUT CONTROL OPTIONS
>>> ; Output frequency for coords (x), velocities (v) and forces (f)
>>> nstxout                  = 5000
>>> nstvout                  = 5000
>>> nstfout                  = 5000
>>> ; Checkpointing helps you continue after crashes
>>> nstcheckpoint            = 5000
>>> ; Output frequency for energies to log file and energy file
>>> nstlog                   = 100
>>> nstenergy                = 100
>>> ; Output frequency and precision for xtc file
>>> nstxtcout                = 500
>>> xtc_precision            = 1000
>>> ; This selects the subset of atoms for the xtc file. You can
>>> ; select multiple groups. By default all atoms will be written.
>>> xtc-grps                 = Protein CA
>>> ; Selection of energy groups
>>> energygrps               = Protein CA SOL
>>>
>>> ; NEIGHBORSEARCHING PARAMETERS
>>> ; nblist update frequency
>>> nstlist                  = 10
>>> ; ns algorithm (simple or grid)
>>> ns_type                  = grid
>>> ; Periodic boundary conditions: xyz (default), no (vacuum)
>>> ; or full (infinite systems only)
>>> pbc                      = xyz
>>> ; nblist cut-off
>>> rlist                    = 0.9
>>> domain-decomposition     = no
>>>
>>> ; OPTIONS FOR ELECTROSTATICS AND VDW
>>> ; Method for doing electrostatics
>>> coulombtype              = PME
>>> rcoulomb_switch          = 0
>>> rcoulomb                 = 0.9
>>> ; Relative dielectric constant for the medium and the reaction field
>>> epsilon_r                = 1
>>> epsilon_rf               = 1
>>> ; Method for doing Van der Waals
>>> vdw-type                 = Cut-off
>>> ; cut-off lengths
>>> rvdw_switch              = 0
>>> rvdw                     = 0.9
>>> ; Apply long range dispersion corrections for Energy and Pressure
>>> DispCorr                 = No
>>> ; Extension of the potential lookup tables beyond the cut-off
>>> table-extension          = 1
>>> ; Seperate tables between energy group pairs
>>> energygrp_table          =
>>> ; Spacing for the PME/PPPM FFT grid
>>> fourierspacing           = 0.12
>>> ; FFT grid size, when a value is 0 fourierspacing will be used
>>> fourier_nx               = 0
>>> fourier_ny               = 0
>>> fourier_nz               = 0
>>> ; EWALD/PME/PPPM parameters
>>> pme_order                = 4
>>> ewald_rtol               = 1e-05
>>> ewald_geometry           = 3d
>>> epsilon_surface          = 0
>>> optimize_fft             = no
>>>
>>> ; GENERALIZED BORN ELECTROSTATICS
>>> ; Algorithm for calculating Born radii
>>> gb_algorithm             = Still
>>> ; Frequency of calculating the Born radii inside rlist
>>> nstgbradii               = 1
>>> ; Cutoff for Born radii calculation; the contribution from atoms
>>> ; between rlist and rgbradii is updated every nstlist steps
>>> rgbradii                 = 2
>>> ; Salt concentration in M for Generalized Born models
>>> gb_saltconc              = 0
>>>
>>> ; IMPLICIT SOLVENT (for use with Generalized Born electrostatics)
>>> implicit_solvent         = No
>>>
>>> ; OPTIONS FOR WEAK COUPLING ALGORITHMS
>>> ; Temperature coupling
>>> Tcoupl                   = berendsen
>>> ; Groups to couple separately
>>> tc_grps                  = Protein Other
>>> ; Time constant (ps) and reference temperature (K)
>>> tau_t                    = 0.1 0.1
>>> ref_t                    = 300 300
>>> ; Pressure coupling
>>> Pcoupl                   = berendsen
>>> Pcoupltype               = isotropic
>>> ; Time constant (ps), compressibility (1/bar) and reference P (bar)
>>> tau_p                    = 1.0
>>> compressibility          = 4.5e-5
>>> ref_p                    = 1.0
>>> ; Random seed for Andersen thermostat
>>> andersen_seed            = 815131
>>>
>>> ; OPTIONS FOR QMMM calculations
>>> QMMM                     = no
>>> ; Groups treated Quantum Mechanically
>>> QMMM-grps                =
>>> ; QM method
>>> QMmethod                 =
>>> ; QMMM scheme
>>> QMMMscheme               = normal
>>> ; QM basisset
>>> QMbasis                  =
>>> ; QM charge
>>> QMcharge                 =
>>> ; QM multiplicity
>>> QMmult                   =
>>> ; Surface Hopping
>>> SH                       =
>>> ; CAS space options
>>> CASorbitals              =
>>> CASelectrons             =
>>> SAon                     =
>>> SAoff                    =
>>> SAsteps                  =
>>> ; Scale factor for MM charges
>>> MMChargeScaleFactor      = 1
>>> ; Optimization of QM subsystem
>>> bOPT                     =
>>> bTS                      =
>>>
>>> ; SIMULATED ANNEALING
>>> ; Type of annealing for each temperature group (no/single/periodic)
>>> annealing                = no no
>>> ; Number of time points to use for specifying annealing in each group
>>> annealing_npoints        =
>>> ; List of times at the annealing points for each group
>>> annealing_time           =
>>> ; Temp. at each annealing point, for each group.
>>> annealing_temp           =
>>>
>>> ; GENERATE VELOCITIES FOR STARTUP RUN
>>> gen_vel                  = yes
>>> gen_temp                 = 300
>>> gen_seed                 = 173529
>>>
>>> ; OPTIONS FOR BONDS
>>> constraints              = all-bonds
>>> ; Type of constraint algorithm
>>> constraint-algorithm     = Lincs
>>> ; Do not constrain the start configuration
>>> unconstrained_start      = no
>>> ; Use successive overrelaxation to reduce the number of shake iterations
>>> Shake-SOR                = no
>>> ; Relative tolerance of shake
>>> shake_tol                = 1e-04
>>> ; Highest order in the expansion of the constraint coupling matrix
>>> lincs-order              = 4
>>> ; Number of iterations in the final step of LINCS. 1 is fine for
>>> ; normal simulations, but use 2 to conserve energy in NVE runs.
>>> ; For energy minimization with constraints it should be 4 to 8.
>>> lincs-iter               = 1
>>> ; Lincs will write a warning to the stderr if in one step a bond
>>> ; rotates over more degrees than
>>> lincs-warnangle          = 30
>>> ; Convert harmonic bonds to morse potentials
>>> morse                    = no
>>>
>>> ; ENERGY GROUP EXCLUSIONS
>>> ; Pairs of energy groups for which all non-bonded interactions are
>>> excluded
>>> energygrp_excl           =
>>>
>>> ; NMR refinement stuff
>>> ; Distance restraints type: No, Simple or Ensemble
>>> disre                    = No
>>> ; Force weighting of pairs in one distance restraint: Conservative or
>>> Equal
>>> disre_weighting          = Equal
>>> ; Use sqrt of the time averaged times the instantaneous violation
>>> disre_mixed              = no
>>> disre_fc                 = 1000
>>> disre_tau                = 1.25
>>> ; Output frequency for pair distances to energy file
>>> nstdisreout              = 100
>>> ; Orientation restraints: No or Yes
>>> orire                    = no
>>> ; Orientation restraints force constant and tau for time averaging
>>> orire-fc                 = 0
>>> orire-tau                = 0
>>> orire-fitgrp             =
>>> ; Output frequency for trace(SD) and S to energy file
>>> nstorireout              = 100
>>> ; Dihedral angle restraints: No, Simple or Ensemble
>>> dihre                    = No
>>> dihre-fc                 = 1000
>>> dihre-tau                = 0
>>> ; Output frequency for dihedral values to energy file
>>> nstdihreout              = 100
>>>
>>> ; Free energy control stuff
>>> free_energy              = no
>>> init_lambda              = 0
>>> delta_lambda             = 0
>>> sc-alpha                 = 0
>>> sc-power                 = 0
>>> sc-sigma                 = 0.3
>>>
>>> ; Non-equilibrium MD stuff
>>> acc-grps                 =
>>> accelerate               =
>>> freezegrps               =
>>> freezedim                =
>>> cos-acceleration         = 0
>>> deform                   =
>>>
>>> ; Electric fields
>>> ; Format is number of terms (int) and for all terms an amplitude (real)
>>> ; and a phase angle (real)
>>> E-x                      =
>>> E-xt                     =
>>> E-y                      =
>>> E-yt                     =
>>> E-z                      =
>>> E-zt                     =
>>>
>>> ; User defined thingies
>>> user1-grps               =
>>> user2-grps               =
>>> userint1                 = 0
>>> userint2                 = 0
>>> userint3                 = 0
>>> userint4                 = 0
>>> userreal1                = 0
>>> userreal2                = 0
>>> userreal3                = 0
>>> userreal4                = 0
>>>
>>>
>>> GROMACS CVS from 2007-04-07
>>> ;
>>> ;	File 'mdout.mdp' was generated
>>> ;	By user: mzink (37571)
>>> ;	On host: beany
>>> ;	At date: Mon Mar 17 20:14:43 2008
>>> ;
>>>
>>> ; VARIOUS PREPROCESSING OPTIONS
>>> title                    =
>>> ; Preprocessor - specify a full path if necessary.
>>> cpp                      = /lib/cpp
>>> include                  =
>>> define                   =
>>>
>>> ; RUN CONTROL PARAMETERS
>>> integrator               = md
>>> ; Start time and timestep in ps
>>> tinit                    = 0
>>> dt                       = 0.002
>>> nsteps                   = 5000
>>> ; For exact run continuation or redoing part of a run
>>> init_step                = 0
>>> ; mode for center of mass motion removal
>>> comm-mode                = Linear
>>> ; number of steps for center of mass motion removal
>>> nstcomm                  = 1
>>> ; group(s) for center of mass motion removal
>>> comm-grps                =
>>>
>>> ; LANGEVIN DYNAMICS OPTIONS
>>> ; Friction coefficient (amu/ps) and random seed
>>> bd-fric                  = 0
>>> ld_seed                  = 1993
>>>
>>> ; ENERGY MINIMIZATION OPTIONS
>>> ; Force tolerance and initial step-size
>>> emtol                    = 0.000001
>>> emstep                   = 0.01
>>> ; Max number of iterations in relax_shells
>>> niter                    = 100
>>> ; Step size (ps^2) for minimization of flexible constraints
>>> fcstep                   = 0
>>> ; Frequency of steepest descents steps when doing CG
>>> nstcgsteep               = 1000
>>> nbfgscorr                = 10
>>>
>>> ; TEST PARTICLE INSERTION OPTIONS
>>> rtpi                     = 0.05
>>>
>>> ; OUTPUT CONTROL OPTIONS
>>> ; Output frequency for coords (x), velocities (v) and forces (f)
>>> nstxout                  = 5000
>>> nstvout                  = 5000
>>> nstfout                  = 5000
>>> ; Checkpointing helps you continue after crashes
>>> nstcheckpoint            = 5000
>>> ; Output frequency for energies to log file and energy file
>>> nstlog                   = 100
>>> nstenergy                = 100
>>> ; Output frequency and precision for xtc file
>>> nstxtcout                = 500
>>> xtc_precision            = 1000
>>> ; This selects the subset of atoms for the xtc file. You can
>>> ; select multiple groups. By default all atoms will be written.
>>> xtc-grps                 = Protein CA
>>> ; Selection of energy groups
>>> energygrps               = Protein CA SOL
>>>
>>> ; NEIGHBORSEARCHING PARAMETERS
>>> ; nblist update frequency
>>> nstlist                  = 10
>>> ; ns algorithm (simple or grid)
>>> ns_type                  = grid
>>> ; Periodic boundary conditions: xyz, no, xy
>>> pbc                      = xyz
>>> periodic_molecules       = no
>>> ; nblist cut-off
>>> rlist                    = 0.9
>>>
>>> ; OPTIONS FOR ELECTROSTATICS AND VDW
>>> ; Method for doing electrostatics
>>> coulombtype              = PME
>>> rcoulomb_switch          = 0
>>> rcoulomb                 = 0.9
>>> ; Relative dielectric constant for the medium and the reaction field
>>> epsilon_r                = 1
>>> epsilon_rf               = 1
>>> ; Method for doing Van der Waals
>>> vdw-type                 = Cut-off
>>> ; cut-off lengths
>>> rvdw_switch              = 0
>>> rvdw                     = 0.9
>>> ; Apply long range dispersion corrections for Energy and Pressure
>>> DispCorr                 = No
>>> ; Extension of the potential lookup tables beyond the cut-off
>>> table-extension          = 1
>>> ; Seperate tables between energy group pairs
>>> energygrp_table          =
>>> ; Spacing for the PME/PPPM FFT grid
>>> ;fourierspacing           = 0.12
>>> ; FFT grid size, when a value is 0 fourierspacing will be used
>>> fourier_nx               = 120
>>> fourier_ny               = 120
>>> fourier_nz               = 120
>>> ; EWALD/PME/PPPM parameters
>>> pme_order                = 4
>>> ewald_rtol               = 1e-05
>>> ewald_geometry           = 3d
>>> epsilon_surface          = 0
>>> optimize_fft             = no
>>>
>>> ; GENERALIZED BORN ELECTROSTATICS
>>> ; Algorithm for calculating Born radii
>>> gb_algorithm             = Still
>>> ; Frequency of calculating the Born radii inside rlist
>>> nstgbradii               = 1
>>> ; Cutoff for Born radii calculation; the contribution from atoms
>>> ; between rlist and rgbradii is updated every nstlist steps
>>> rgbradii                 = 2
>>> ; Salt concentration in M for Generalized Born models
>>> gb_saltconc              = 0
>>>
>>> ; IMPLICIT SOLVENT (for use with Generalized Born electrostatics)
>>> implicit_solvent         = No
>>>
>>> ; OPTIONS FOR WEAK COUPLING ALGORITHMS
>>> ; Temperature coupling
>>> Tcoupl                   = berendsen
>>> ; Groups to couple separately
>>> tc_grps                  = Protein Other
>>> ; Time constant (ps) and reference temperature (K)
>>> tau_t                    = 0.1 0.1
>>> ref_t                    = 300 300
>>> ; Pressure coupling
>>> Pcoupl                   = berendsen
>>> Pcoupltype               = isotropic
>>> ; Time constant (ps), compressibility (1/bar) and reference P (bar)
>>> tau_p                    = 1.0
>>> compressibility          = 4.5e-5
>>> ref_p                    = 1.0
>>> ; Scaling of reference coordinates, No, All or COM
>>> refcoord_scaling         = No
>>> ; Random seed for Andersen thermostat
>>> andersen_seed            = 815131
>>>
>>> ; OPTIONS FOR QMMM calculations
>>> QMMM                     = no
>>> ; Groups treated Quantum Mechanically
>>> QMMM-grps                =
>>> ; QM method
>>> QMmethod                 =
>>> ; QMMM scheme
>>> QMMMscheme               = normal
>>> ; QM basisset
>>> QMbasis                  =
>>> ; QM charge
>>> QMcharge                 =
>>> ; QM multiplicity
>>> QMmult                   =
>>> ; Surface Hopping
>>> SH                       =
>>> ; CAS space options
>>> CASorbitals              =
>>> CASelectrons             =
>>> SAon                     =
>>> SAoff                    =
>>> SAsteps                  =
>>> ; Scale factor for MM charges
>>> MMChargeScaleFactor      = 1
>>> ; Optimization of QM subsystem
>>> bOPT                     =
>>> bTS                      =
>>>
>>> ; SIMULATED ANNEALING
>>> ; Type of annealing for each temperature group (no/single/periodic)
>>> annealing                = no no
>>> ; Number of time points to use for specifying annealing in each group
>>> annealing_npoints        =
>>> ; List of times at the annealing points for each group
>>> annealing_time           =
>>> ; Temp. at each annealing point, for each group.
>>> annealing_temp           =
>>>
>>> ; GENERATE VELOCITIES FOR STARTUP RUN
>>> gen_vel                  = yes
>>> gen_temp                 = 300
>>> gen_seed                 = 173529
>>>
>>> ; OPTIONS FOR BONDS
>>> constraints              = all-bonds
>>> ; Type of constraint algorithm
>>> constraint-algorithm     = Lincs
>>> ; Do not constrain the start configuration
>>> continuation             = yes
>>> ; Use successive overrelaxation to reduce the number of shake iterations
>>> Shake-SOR                = no
>>> ; Relative tolerance of shake
>>> shake_tol                = 1e-04
>>> ; Highest order in the expansion of the constraint coupling matrix
>>> lincs-order              = 4
>>> ; Number of iterations in the final step of LINCS. 1 is fine for
>>> ; normal simulations, but use 2 to conserve energy in NVE runs.
>>> ; For energy minimization with constraints it should be 4 to 8.
>>> lincs-iter               = 1
>>> ; Lincs will write a warning to the stderr if in one step a bond
>>> ; rotates over more degrees than
>>> lincs-warnangle          = 30
>>> ; Convert harmonic bonds to morse potentials
>>> morse                    = no
>>>
>>> ; ENERGY GROUP EXCLUSIONS
>>> ; Pairs of energy groups for which all non-bonded interactions are
>>> excluded
>>> energygrp_excl           =
>>>
>>> ; WALLS
>>> ; Number of walls, type, atom types, densities and box-z scale factor
>>> for
>>> Ewald
>>> nwall                    = 0
>>> wall_type                = 9-3
>>> wall_atomtype            =
>>> wall_density             =
>>> wall_ewald_zfac          = 3
>>>
>>> ; COM PULLING
>>> ; Pull type: no, umbrella, constraint, constant_force
>>> pull                     = no
>>>
>>> ; NMR refinement stuff
>>> ; Distance restraints type: No, Simple or Ensemble
>>> disre                    = No
>>> ; Force weighting of pairs in one distance restraint: Conservative or
>>> Equal
>>> disre_weighting          = Equal
>>> ; Use sqrt of the time averaged times the instantaneous violation
>>> disre_mixed              = no
>>> disre_fc                 = 1000
>>> disre_tau                = 1.25
>>> ; Output frequency for pair distances to energy file
>>> nstdisreout              = 100
>>> ; Orientation restraints: No or Yes
>>> orire                    = no
>>> ; Orientation restraints force constant and tau for time averaging
>>> orire-fc                 = 0
>>> orire-tau                = 0
>>> orire-fitgrp             =
>>> ; Output frequency for trace(SD) and S to energy file
>>> nstorireout              = 100
>>> ; Dihedral angle restraints: No, Simple or Ensemble
>>> dihre                    = No
>>> dihre-fc                 = 1000
>>> dihre-tau                = 0
>>> ; Output frequency for dihedral values to energy file
>>> nstdihreout              = 100
>>>
>>> ; Free energy control stuff
>>> free_energy              = no
>>> init_lambda              = 0
>>> delta_lambda             = 0
>>> sc-alpha                 = 0
>>> sc-power                 = 0
>>> sc-sigma                 = 0.3
>>>
>>> ; Non-equilibrium MD stuff
>>> acc-grps                 =
>>> accelerate               =
>>> freezegrps               =
>>> freezedim                =
>>> cos-acceleration         = 0
>>> deform                   =
>>>
>>> ; Electric fields
>>> ; Format is number of terms (int) and for all terms an amplitude (real)
>>> ; and a phase angle (real)
>>> E-x                      =
>>> E-xt                     =
>>> E-y                      =
>>> E-yt                     =
>>> E-z                      =
>>> E-zt                     =
>>>
>>> ; User defined thingies
>>> user1-grps               =
>>> user2-grps               =
>>> userint1                 = 0
>>> userint2                 = 0
>>> userint3                 = 0
>>> userint4                 = 0
>>> userreal1                = 0
>>> userreal2                = 0
>>> userreal3                = 0
>>> userreal4                = 0
>>>
>>>
>>>
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>>
> 
> 
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-- 
David van der Spoel, Ph.D.
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se



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