The torsional potential you compute from the equation, is NOT and can
never be the same as the difference between potential energies.
The difference in potential energies includes changes in vdw and
electrostatics, etc.
You need to read some early paper on force fields and what each term
represents.
adrian
On 6/17/12 12:01 AM, Takeshi Baba wrote:
> Hi ,
>
> I have some problems when preparing the Force Field.
>
> I study the force field to make new force parameter.
>
> First of all, I tried to reproduce the Cl-CT-CT-Cl parameter.
>
> But I couldn't reproduce the parameter
>
> The parameter(Cl-CT-CT-Cl) is " 1 0.45 180.0 1" in the parm99.dat
>
> So E( Cl-CT-CT-C) = 0.5*0.45(1+cos(x-180))
>
> when x=180 ,E( Cl-CT-CT-C) = 0.45 kcal/mol
>
> In my case, the maximal potential energy difference is 20 kcal/mol.
>
>
> I tried to investigate various pattern to prepare Cl-CT-CT-Cl parameter.
>
> But I couldn't.
>
> Maybe, I think something wrong with my calculation.
>
> Please give me some advice to prepare the parameter.
>
>
>
> Thank you
>
> Takeshi Baba
>
> --------------------------------------------------------------------------------------------------------
> Takeshi Baba
> Division of Chemical Engineering,
> Department of Materials Engineering Science,
> Graduate School of Engineering Science,
> Osaka University, Toyonaka, Osaka 560-8531, JAPAN
> Tel: +81-6-6850-6265, Fax: +81-6-6850-6268
> E-mail: tbaba.cheng.es.osaka-u.ac.jp
> --------------------------------------------------------------------------------------------------------
>
>
>
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--
Dr. Adrian E. Roitberg
Professor
Quantum Theory Project, Department of Chemistry
University of Florida
roitberg.ufl.edu
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Received on Sat Jun 16 2012 - 22:30:02 PDT
