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 - 00:30:03 PST
