Re: Force field design

From: Kenno Vanommeslaeghe (
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.
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:

Christopher Mayne's advice in this thread is sound.

This archive was generated by hypermail 2.1.6 : Thu Dec 31 2015 - 23:21:00 CST