Dear Francois,
Thank you for your reply. I will do as suggested to find a RESP charge for OPLS.
Then how can I get the LJ parameters between those 'GAFF-particles' and 'OPLS-particles' since they are using two kinds of combine rules?
Sincerely,
Guoxiong
On Feb 21, 2012, at 10:27 AM, FyD wrote:
> Dear Guoxiong Su,
>
> Mixing two force fields is always dangerous.
>
> I would compute a highly consistent set of charges for all the
> molecules to be studied. If you want to use OPLS you can find a RESP
> approach for OPLS.
> See R. H. Henchman and J. W. Essex, J. Comput. Chem., 1999, 20, 483?498.
> This approach should be easy to implement in the R.E.D. program.
>
> A new box for benzonitrile can be created for Amber.... Then, whatever
> you decide to use (may be try first SCNB = 2.0 & SCEE = 1.2) your
> benzonitrile box has to be tested/studied...
>
> regards, Francois
>
>
>> I am trying to solvate a molecular triad in a benzonitrile box. For
>> this molecular triad, I used Antechamber to generate the topology
>> file with GAFF. The charge is calculated using AM1-BCC. I have done
>> some literature search and I found OPLS force filed has the
>> parameters for benzonitrile. Is it reasonable to mix GAFF with OPLS
>> force field in AMBER?
>>
>> I have read though the mailing list and I found some people was
>> mixing AMBER force field with the Glycam force field (e.g.
>> http://archive.ambermd.org/200906/0240.html). I knew that for GAFF,
>> SCNB = 2.0 and SCEE = 1.2. What values are they in OPLS? Is it 1.0
>> since OPLS doesn't have any scaling? The combine rules of GAFF and
>> OPLS for the Lennard-Jones potentials are different as well. GAFF
>> follows the AMBER rules and OPLS uses geometric mean for sigma and
>> epsilon. Is it possible to use two kinds of combine rules in AMBER?
>
>
>
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Received on Tue Feb 21 2012 - 09:00:03 PST
