[gmx-users] error about pbc

Tsjerk Wassenaar tsjerkw at gmail.com
Mon Jan 28 04:19:23 CET 2013


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
>>>>> 2500 University Drive NW
>>>>> Calgary, AB T2N 1N4
>>>>> Canada
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>>>>>  --
>>> ==============================****==========
>>>
>>> Justin A. Lemkul, Ph.D.
>>> Research Scientist
>>> Department of Biochemistry
>>> Virginia Tech
>>> Blacksburg, VA
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>>> http://www.bevanlab.biochem.****vt.edu/Pages/Personal/justin<http://vt.edu/Pages/Personal/justin>
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>>> >
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> --
> ==============================**==========
>
>
> Justin A. Lemkul, Ph.D.
> Research Scientist
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> jalemkul[at]vt.edu | (540) 231-9080
> http://www.bevanlab.biochem.**vt.edu/Pages/Personal/justin<http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin>
>
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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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