[gmx-users] genconf

[Justin A. Lemkul]

Payman Pirzadeh wrote:
> In my previous e-mail, I posted the amount of charge given by GROMACS:
> 
>> NOTE 2 [file sixsitemodel.top, line 8]:
>>
>>   System has non-zero total charge: -1.220703e-04
> 
> Also, I run the system without multiplication, and it runs fine without any
> notes on the presence of a net charge!!! But, as soon as it is multiplied,
> then it gives notes of net charge!
> 

Then I'm more confused (and hence why I asked the first time).  You said your 
original system had a non-zero charge.  Now you say that there were no notes 
about net charge, so the original system was uncharged.

Depending on the size of your system, small rounding errors can accumulate and 
cause tiny fractional charges.  I don't know if this is problematic or not (in 
terms of the system charge that mdrun finds), but it could be why you are seeing 
this note.

-Justin

> Payman
> 
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: gmx-users-bounces at gromacs.org [mailto:gmx-users-bounces at gromacs.org]
> On Behalf Of Justin A. Lemkul
> Sent: July 21, 2009 6:13 PM
> To: Discussion list for GROMACS users
> Subject: Re: [gmx-users] genconf
> 
> 
> 
> Payman Pirzadeh wrote:
>> OK! Thanks for the tips on thermostat.
>>
>> I multiplied my .gro file by using the command "genconf". My original 
>> box has non-zero charge, but the generated bigger box has some charges:
>>
>>  
> 
> Define "non-zero."  Is it at least an integer?  Should your system bet net 
> neutral at this stage in your system preparation?
> 
> -Justin
> 
>> NOTE 2 [file sixsitemodel.top, line 8]:
>>
>>   System has non-zero total charge: -1.220703e-04
>>
>>  
>>
>> Then, during minimization, the system experiences a large positive 
>> potential and infinite force. Is there a technicality in using "genconf" 
>> that I am missing? Doesn't it read the dimensions of the box from .gro 
>> file to make sure no particles are overlapping with the original box? Or 
>> no particle is coming from the new one in the old one?
>>
>>  
>>
>> Payman
>>
>>  
>>
>> *From:* gmx-users-bounces at gromacs.org 
>> [mailto:gmx-users-bounces at gromacs.org] *On Behalf Of *Vitaly V. Chaban
>> *Sent:* July 21, 2009 4:53 PM
>> *To:* gmx-users at gromacs.org
>> *Subject:* [gmx-users] Re: reliability of NOTES
>>
>>  
>>
>>
>>     Hello,
>>     I am trying to prepare the input files for an MD run. After running
>>     grompp,
>>     I received the following note:
>>
>>     NOTE 1 [file npt.mdp, line unknown]:
>>      The Berendsen thermostat does not generate the correct kinetic energy
>>      distribution. You might want to consider using the V-rescale
>>     thermostat.
>>
>>     How reliable this note is?
>>
>>
>> It's true.
>>  
>>
>>     And how can I implement V-rescale thermostat in y
>>     input file (I found nothing in the manual).
>>
>>
>> Substitute "berendsen" with "V-rescale" in the mdp file.
>>
>>
>>     Also, when I changed the thermostat to nose-hoover, it said that it
>>     can not
>>     be used with Berendsen barostat. Why?
>>
>> C'est la vie...
>>
>>
>> -- 
>> Vitaly V. Chaban, Ph.D. (ABD)
>> School of Chemistry
>> V.N. Karazin Kharkiv National University
>> Svoboda sq.,4, Kharkiv 61077, Ukraine
>> email: chaban at univer.kharkov.ua 
>> <mailto:chaban at univer.kharkov.ua>,vvchaban at gmail.com 
>> <mailto:vvchaban at gmail.com>
>> skype: vvchaban, mob.: +38-097-8259698
>> http://www-rmn.univer.kharkov.ua/chaban.html
>> ===================================
>> !!! Looking for a postdoctoral position !!!
>> ===================================
>>
>>
>> ------------------------------------------------------------------------
>>
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> 

-- 
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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