[gmx-users] error about pbc

Kieu Thu Nguyen kieuthu2212 at gmail.com
Mon Jan 28 06:53:02 CET 2013


Thank Justin and Tsjerk so much for your help !
I will try smaller time step. And i hope it work :-)

Regards,
KT


On Mon, Jan 28, 2013 at 10:19 AM, Tsjerk Wassenaar <tsjerkw at gmail.com>wrote:

> Well, 20-30 fs is fine with Martini. But you may have to take care
> initially, and start with a smaller time step.
>
> Cheers,
>
> Tsjerk
>
> On Mon, Jan 28, 2013 at 3:11 AM, Justin Lemkul <jalemkul at vt.edu> wrote:
>
> >
> >
> > On 1/27/13 12:15 PM, Kieu Thu Nguyen wrote:
> >
> >> @Justin,
> >> Fmax=8.0226669e+00
> >>
> >
> > OK, that looks good.
> >
> >
> >  the system includes protein, lipid, water, ion Cl-
> >>
> >> em.mdp file is
> >>
> >> integrator               = steep
> >> tinit                    = 0.0
> >> dt                       = 0.02
> >> nsteps                   = 50000
> >> nstcomm                  = 1
> >> nstxout                  = 5000
> >> nstvout                  = 5000
> >> nstfout                  = 0
> >> nstlog                   = 1000
> >> nstenergy                = 1000
> >> nstxtcout                = 1000
> >> xtc_precision            = 1000
> >> nstlist                  = 1
> >> ns_type                  = grid
> >> pbc                      = xyz
> >> rlist                    = 1.4
> >> coulombtype              = Shift
> >> rcoulomb_switch          = 0.0
> >> rcoulomb                 = 1.2
> >> epsilon_r                = 15
> >> vdw_type                 = Shift
> >> rvdw_switch              = 0.9
> >> rvdw                     = 1.2
> >> DispCorr                 = No
> >> tcoupl                   = no
> >> pcoupl                   = no
> >> gen_vel                  = no
> >> constraints              = none
> >> constraint_algorithm     = Lincs
> >> continuation         = no
> >> lincs_order              = 4
> >> lincs_warnangle          = 30
> >>
> >>
> >> equi.mdp file is
> >>
> >> integrator               = md
> >> tinit                    = 0.0
> >> dt                       = 0.03
> >>
> >
> > Does a smaller time step work?  I know the whole point of a MARTINI
> > simulation is to use a 20-40 fs time step, but in my (very very limited)
> > experience, nothing over 20 fs is consistently stable.  Perhaps others
> with
> > better experience can offer pointers.
> >
> > -Justin
> >
> >
> >  nsteps                   = 3000000
> >> nstcomm                  = 1
> >> comm-grps         =
> >> nstxout                  = 5000
> >> nstvout                  = 5000
> >> nstfout                  = 0
> >> nstlog                   = 1000
> >> nstenergy                = 1000
> >> nstxtcout                = 1000
> >> xtc_precision            = 100
> >> xtc-grps                 =
> >> energygrps               =
> >> nstlist                  = 10
> >> ns_type                  = grid
> >> pbc                      = xyz
> >> rlist                    = 1.2
> >> coulombtype              = Shift
> >> rcoulomb_switch          = 0.0
> >> rcoulomb                 = 1.2
> >> epsilon_r                = 15
> >> vdw_type                 = Shift
> >> rvdw_switch              = 0.9
> >> rvdw                     = 1.2
> >> DispCorr                 = No
> >> tcoupl                   = Berendsen
> >> tc-grps                  = Protein DSPC Ion_W
> >> tau_t                    = 1.5 1.5 1.5
> >> ref_t                    = 310 310 310
> >> Pcoupl                   = Berendsen
> >> Pcoupltype               = semiisotropic
> >> tau_p                    = 3.0 3.0
> >> compressibility          = 3e-4 3e-4
> >> ref_p                    = 1.0 1.0
> >> gen_vel                  = no
> >> constraints              = none
> >> constraint_algorithm     = Lincs
> >> continuation             = no
> >> lincs_order              = 4
> >> lincs_warnangle          = 30
> >>
> >> Thanks so much for any help !
> >> Regards,
> >> KT
> >>
> >>
> >> On Sun, Jan 27, 2013 at 8:26 AM, Justin Lemkul <jalemkul at vt.edu> wrote:
> >>
> >>
> >>>
> >>> On 1/26/13 8:17 PM, Kieu Thu Nguyen wrote:
> >>>
> >>>  Thank Tsjerk so much !
> >>>> But after being minimized 50000 steps and equilibrated 90 ns, there
> are
> >>>> some bonds in the system that rotate more than 30 degrees.
> >>>> I applied tips for blew up system as you advised. But the system does
> >>>> not
> >>>> achieve balance.
> >>>> Should i carry out more many steps for minimization ? or minimize many
> >>>> times ? to get more equilibrated system.
> >>>>
> >>>>
> >>>>  I would say that 50000 steps of minimization is far more than is
> >>> normally
> >>> necessary.  What Fmax do you achieve at the end of EM?  What is in the
> >>> system? What is in your .mdp file?  Systems can randomly crash if the
> >>> model
> >>> physics breaks due to incorrect .mdp settings or an unstable topology.
> >>>
> >>> -Justin
> >>>
> >>>
> >>>   On Thu, Jan 24, 2013 at 11:13 PM, Tsjerk Wassenaar <
> tsjerkw at gmail.com
> >>>
> >>>> wrote:
> >>>>>
> >>>>
> >>>>   Hi KT,
> >>>>
> >>>>>
> >>>>> This is caused by another problem. Your system blew up. Check
> messages
> >>>>> before this one, and check the log for LINCS warnings.
> >>>>>
> >>>>> Cheers,
> >>>>>
> >>>>> Tsjerk
> >>>>>
> >>>>> On Thu, Jan 24, 2013 at 9:11 AM, Kieu Thu Nguyen <
> >>>>> kieuthu2212 at gmail.com
> >>>>>
> >>>>>  wrote:
> >>>>>>
> >>>>>>
> >>>>>   Dear All,
> >>>>>
> >>>>>>
> >>>>>> My MD simulation  has an error
> >>>>>>
> >>>>>> Warning: Only triclinic boxes with the first vector parallel to the
> >>>>>>
> >>>>>>  x-axis
> >>>>>
> >>>>>  and the second vector in the xy-plane are supported.
> >>>>>>            Box (3x3):
> >>>>>>               Box[    0]={         nan,          nan,          nan}
> >>>>>>               Box[    1]={         nan,          nan,          nan}
> >>>>>>               Box[    2]={         nan,          nan,          nan}
> >>>>>>            Can not fix pbc.
> >>>>>>
> >>>>>> I searched on Gromacs-errors web, but i did not see this error.
> >>>>>> How can i fix it ?
> >>>>>>
> >>>>>> Thanks and regards,
> >>>>>> KT
> >>>>>> --
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> >>>>> Tsjerk A. Wassenaar, Ph.D.
> >>>>>
> >>>>> post-doctoral researcher
> >>>>> Biocomputing Group
> >>>>> Department of Biological Sciences
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> >>>>>  --
> >>> ==============================****==========
> >>>
> >>> Justin A. Lemkul, Ph.D.
> >>> Research Scientist
> >>> Department of Biochemistry
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> >
> > Justin A. Lemkul, Ph.D.
> > Research Scientist
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> > Virginia Tech
> > Blacksburg, VA
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> --
> Tsjerk A. Wassenaar, Ph.D.
>
> post-doctoral researcher
> Biocomputing Group
> Department of Biological Sciences
> 2500 University Drive NW
> Calgary, AB T2N 1N4
> Canada
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