Hi Francois:
Thanks again for such detailed explanations. I do learned a lot these
days. I will try it recently.
Best wishes & nice weekend
Albert
On 12/02/2011 09:02 AM, FyD wrote:
> Dear Albert,
>
>> I've got another question about the partial charge calculation in
>> AMBER. I found that it use RESP for HF/6-31G* for Amber FF. I am
>> wondering, is CHARMM 27 or CHARMM36 use the same methods for partial
>> charge calculation? I may also use CHARMM FF in amber in the near future.
> CHARMM FF do not use RESP charges; See for instance, the following
> tutorial: http://mackerell.umaryland.edu/~kenno/tutorial/
> It seems that RESP charges are only for AMBER FF although a RESP model
> for OPLS does exist: it even uses the RESP program from the AMBER
> distribution. See
> http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1096-987X(19990415)20:5%3C483::AID-JCC2%3E3.0.CO;2-4/abstract
>
> Then, once this is said, you find many articles in the literature
> where CHARMM users and even developers DO use molecular electrostatic
> potential (MEP)-based charges.
>
> R.E.D. III.x and R.E.D. Server/R.E.D. IV do not only derive RESP
> charges; but are able to derive ESP charges based on different
> algorithms (CHELPG, Connolly surface; if you use GAMESS you could
> modify the source code and use the GEODESIC algo. by Spackman) for the
> grid of points in MEP computation.
> See
> http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1096-987X(19960115)17:1%3C1::AID-JCC1%3E3.0.CO;2-V/abstract
>
> Whatever the charge model you will select - you will have to
> demonstrate that it is suitable for your problem. If you do use a
> CHARMM FF, I would start by using the CHELPG algo and ESP charges;
> i.e. the ESP-C1 charge model in R.E.D.; if you use R.E.D. Server
> Development you will be able to use the ESP-Y1 charge model.
> See http://q4md-forcefieldtools.org/REDS-Development/popup/popkeyword.php
> We plan to release more "user defined options" in R.E.D. Server
> development - letting users to choose between various basis sets in
> the geometry optimization and MEP computation steps... You can also
> easily modify the source code of R.E.D. III.x and include the basis
> set and theory level of you choice; if you do not know how to do it;
> just ask in the Amber or q4md-fft mailing list and we will do it for
> you.
>
> regards, Francois
>
>
>
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Received on Fri Dec 02 2011 - 01:30:03 PST
