Re: Force field design

From: Kenno Vanommeslaeghe (kvanomme_at_rx.umaryland.edu)
Date: Wed Jul 16 2014 - 12:24:29 CDT

On 07/15/2014 12:55 PM, Abhishek TYAGI wrote:
> 1. I tried CGenFF and got a *.str file but the data in the file is different from my input file i.e. mol2 file, the pdb format is different from the *.str file.

The str file contains a force field for your molecule, while the mol2 and
pdb formats contain a geometry. How could the data not be different???

The str file is a concatenated topology and parameter file. NAMD knows to
ignore the topology section and can read the file as it is.
http://mackerell.umaryland.edu/~kenno/cgenff/program.html#namd
I believe psfgen does the same (read the topology and ignore the
parameters) though I'm less sure about that.

> 2. I tried to get force field from swissparam website and received the different file as *.par, *.top file, I tried MD on this field it runs successful, but the question is that is this correct approach?

It is strongly encouraged to search the archive before posting a question.
If you had, you would have discovered the use of SwissParam for
condensed-phase calculations is discouraged, and found advise on better
ways to do it:
http://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2013-2014/0846.html
http://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2013-2014/0893.html
http://www.ks.uiuc.edu/Research/namd/mailing_list/namd-l.2013-2014/1250.html

Christopher Mayne's advice in this thread is sound.

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