[gmx-users] vacuum right but melt collapse

kitty ji jiqing at iccas.ac.cn
Wed Mar 7 02:43:31 CET 2007

Thanks Mark.
But when one polymer chain was used, non-bonded interaction has already been there. Because one chain means C44H156O22.
After all, I'd like to try more chains.

Message: 1
Date: Tue, 06 Mar 2007 17:01:52 +1100
From: Mark Abraham <Mark.Abraham at anu.edu.au>
Subject: Re: [gmx-users] vacuum right but melt collapse
To: Discussion list for GROMACS users <gmx-users at gromacs.org>
Message-ID: <45ED03D0.6010803 at anu.edu.au>
Content-Type: text/plain; charset=GB2312

kitty ji wrote:
> Hi GMX user:
> A model for Poly(vinyl methyl ether) was built with OPLS force field ( 
> all H ).
> When the model was run alone (a single chain) in vacuum, anything goes ok.
> But with 45 chains box, the system will be collapse with a little bond 
> elongates abnormal whatever in NVT or NPT.
> The relax time of pressure and temperature were adjust but no helpful.
> How can I found some possible reason and then fix it ? Any advise will 
> be appreciated.

If an isolated molecule doesn't do anything strange, and two more more
do, then you have a problem with inter-molecular interactions, i.e. the
non-bonded ones. Try with just 2 chains to verify this... and look
carefully at the atom types and the non-bonded parameters for them.


Ji Qing
Institute of Chemistry, Chinese Academy of Sciences
Tel: 0086-10-62562894  ,82618423
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