Hi,

I minimized without restraints, could that be the problem?
After the minimization I got a Potential Energy  = -6.1434351e+02.

Gadi


Quoting "Justin A. Lemkul" <[EMAIL PROTECTED]>:

Quoting [EMAIL PROTECTED]:

Hi,

The full mdrun output when the simulation blows up is:

Step 0, time 0 (ps)  LINCS WARNING
relative constraint deviation after LINCS:
max inf (between atoms 6 and 7) rms inf
bonds that rotated more than 30 degrees:
          .
          .
          .
Warning: 1-4 interaction between 1 and 6 at distance
324490777485109120.000 which is larger than the 1-4 table size 1.000 nm
These are ignored for the rest of the simulation
This usually means your system is exploding,
if not, you should increase table-extension in your mdp file

Basic information about this type of error can be found here (as well as several
hundred posts in the list archive):

http://wiki.gromacs.org/index.php/Errors#LINCS_warnings

How did you do your minimization, with or without restraints? Did it converge
to an acceptable potential energy?

-Justin


Thanks Gadi

Quoting "Justin A. Lemkul" <[EMAIL PROTECTED]>:

>
> Did your minimization converge to a nice, negative potential energy?
>   Also, what
> is the full mdrun output when the simulation blows up?  You've
> quoted the last
> bit, but it would be more informative to see the whole output, or at least
a
> description of it (i.e., LINCS warnings).
>
> -Justin
>
> Quoting [EMAIL PROTECTED]:
>
>>
>> Hi,
>>
>> I tried using no temperature coupling and no constraints, that did not
help.
>> If I run the simulation without the position restraints it works OK.
>> Could there by something wrong with the posre file (I'll attach it at
>> the end of the email).
>> I want one of the atoms in the lipid to stay in one place and the rest
>> to wiggle around it. Is there any other way to do that which is not
>> position restraints.
>>
>> Thanks Gadi
>>
>>
>> [ position_restraints ]
>> ; atom  type      fx      fy      fz
>>       1     1  0  0  0
>>       2     1  0  0  0
>>       3     1  0  0  0
>>       4     1  0  0  0
>>       5     1  0  0  0
>>       6     1  0  0  0
>>       7     1  0  0  0
>>       8     1  1000.0  1000.0  1000.0
>>       9     1  0  0  0
>>      10     1  0  0  0
>>      11     1  0  0  0
>>      12     1  0  0  0
>>      13     1  0  0  0
>>      14     1  0  0  0
>>      15     1  0  0  0
>>      16     1  0  0  0
>>      17     1  0  0  0
>>      18     1  0  0  0
>>      19     1  0  0  0
>>      20     1  0  0  0
>>      21     1  0  0  0
>>      22     1  0  0  0
>>      23     1  0  0  0
>>      24     1  0  0  0
>>      25     1  0  0  0
>>      26     1  0  0  0
>>      27     1  0  0  0
>>      28     1  0  0  0
>>      29     1  0  0  0
>>      30     1  0  0  0
>>      31     1  0  0  0
>>      32     1  0  0  0
>>      33     1  0  0  0
>>      34     1  0  0  0
>>      35     1  0  0  0
>>      36     1  0  0  0
>>      37     1  0  0  0
>>      38     1  0  0  0
>>      39     1  0  0  0
>>      40     1  0  0  0
>>      41     1  0  0  0
>>      42     1  0  0  0
>>      43     1  0  0  0
>>      44     1  0  0  0
>>      45     1  0  0  0
>>      46     1  0  0  0
>>      47     1  0  0  0
>>      48     1  0  0  0
>>      49     1  0  0  0
>>      50     1  0  0  0
>>
>> Quoting Mark Abraham <[EMAIL PROTECTED]>:
>>
>> > [EMAIL PROTECTED] wrote:
>> >
>> > Please generate replies to the mailing list sensibly. It's very hard to
>> > work out who you are quoting where in this email. It'd be easy just to
>> > ignore it, and that's the last thing you should want.
>> >
>> >> Hello,
>> >>
>> >> I'm trying to run a simulation with one lipid molecule in a fixed
>> >> simulation box without pbc.
>> >> I set position restraints on one of the atoms and I seem to keep on
>> >> getting the following error:
>> >
>> > Why do you want MD of a single lipid and a position restraint on one
>> > atom? If you just want to see a lipid wiggle around, then don't create
>> > more numerical complexity.
>> >
>> >> The lipid is DPPC.The .itp file I got from a coworker that used it
>> >> before for membrane MD simulations.
>> >> To minimize the system I used steepest descent with the following
>> >> parameters:
>> >
>> > Well if your grompp and mdrun completed successfully and without
>> > warnings then you've probably got an OK topology and structure.
>> >
>> > The combination of all bond constraints, a single lipid in vacuo,
>> > temperature coupling and a single position restraint sounds like a
>> > recipe for a numerical disaster, i.e. blowing up. Try with fewer of
>> > those things applied, or get a more physically-reasonable system, like
>> > a whole membrane.
>> >
>> > Mark
>> > _______________________________________________
>> > gmx-users mailing list    gmx-users@gromacs.org
>> > http://www.gromacs.org/mailman/listinfo/gmx-users
>> > Please search the archive at http://www.gromacs.org/search before
posting!
>> > Please don't post (un)subscribe requests to the list. Use the www
>> > interface or send it to [EMAIL PROTECTED]
>> > Can't post? Read http://www.gromacs.org/mailing_lists/users.php
>>
>>
>>
>> ----------------------------------------------------------------
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>>
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>
>
>
> ========================================
>
> Justin A. Lemkul
> Graduate Research Assistant
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> [EMAIL PROTECTED] | (540) 231-9080
> http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/
>
> ========================================
> _______________________________________________
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========================================

Justin A. Lemkul
Graduate Research Assistant
Department of Biochemistry
Virginia Tech
Blacksburg, VA
[EMAIL PROTECTED] | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/

========================================
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