I didn't see anything inherently wrong with your previous observations, so I suspect your new approach is probably fine. There are several ways to do just about anything; you just need to find one that works to your satisfaction and represents a reasonable model of whatever you're trying to simulate.

-Justin

On 10/15/12 12:37 PM, mohammad agha wrote:
Dear Justin,

The previous problems was as is following:

Dear GROMACS Users,

I asked this question before but I don't understand it!



  I placed several materials in my box of simulation for example box with
  6nm*6nm*6nm and my materials are not placed in the smaller box but when
  I equilibrate my system, the box became smaller and temperature and
pressure also equilibrate. my question is: is my system and equilibrate
mistake, because of reach to smaller box? Is there equilibriums with
reach to smaller box?



What do you mean by "my materials are not placed in the smaller box"?

If a box compresses, it is because the initial configuration was incompatible
with the desired equilibration conditions and it contracted produce the desired
quantity (likely pressure).

-Justin

Dear Justin,

"my materials are not placed in the
smaller box" means if I select box with dimensions 5.99 nm, space is low
  and insufficient for my molecules! but after equilibrate the box become
  small.

Please define what you mean here.  You start with a 6-nm
cubic box.  How small does it get?  Are the box vectors trending
downward, or do they converge?  What is the change in density, and is it
  acceptable?

According what you said, when the box become smaller in equilibrium, there is 
not mistake and it is natural?


That
  depends on the magnitude of the change.  Compression indicates that the
  pressure (and thus density of the system) was not at the desired value
and the system is contracting.  The manner in which the contraction
occurs (magnitude, speed) is the deciding factor as to whether or not
there is a problem.

also,


Dear Mark,


May I know your idea about cause of my doubt, Please?

As I said yesterday:

At least one of your volume, contents or model physics are not
consistent with the others, but only you can say which.

Since only you know anything about your volume, contents and model
physics, or that of the work you think you should be replicating, we
can't help at the moment. See previous comment about relevant
information :-)

Mark


Best Regards
Sara



----- Original Message -----
From: Mark Abraham <[email protected]>
To: Discussion list for GROMACS users <[email protected]>
Cc:
Sent: Friday, October 5, 2012 9:34 AM
Subject: Re: [gmx-users] equilibrium for box of simulation

On 5/10/2012 3:55 PM, mohammad agha wrote:
Dear Justin,

Thank you very much.
So, decreasing of box dimensions is not bad, if all thing process natural, yes?

  The cause of my doubt was because of in the most of articles was said
for example " we select box with dimensions 10nm that after equilibrium
was converted to 11nm" and I didn't see the report of decreasing of box
dimensions! May I know your idea about it, Please?
Following a
published method closely and observing an opposite result is a cause for
  concern. You have to judge "closely," however. You should have said
earlier this was one of your reasons for doubt, rather than leave us to
guess. The quality of the help you might receive is often in direct
proportion to the quantity of relevant information you give in asking
for it.

Mark


----- Forwarded Message -----
From: Justin Lemkul <[email protected]>
To: mohammad agha <[email protected]>; Discussion list for GROMACS users 
<[email protected]>
Cc:
Sent: Monday, October 15, 2012 7:50 PM
Subject: Re: [gmx-users] about equilibrium



On 10/15/12 12:11 PM, mohammad agha wrote:


Dear Justin,

Thank you very much from your response. This question was because of my previous problems 
about equilibration the box that I sent it with subject "equilibrium for box of 
simulation". When I equilibrate solvent and additives separated and then add to 
surfactant and after that equilibrate totally, there are not previous problems and I 
wanted to know that this method is correct?


Please provide a link to the previous thread.  I read hundreds of posts per
week; I don't recall this one.  A sequence of commands would also be helpful
here, as I cannot clearly envision what you are describing.

-Justin


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

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

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