From: Leonardo Sepulveda Durán (leonardosepulveda_at_gmail.com)
Date: Tue Jun 21 2005 - 12:42:07 CDT
Yesterday I read the 1997 F3C Levitt's paper. In table 3 a comparison
to other published 3 point models. TIP3P is far one of the worst
models, it have a Diffusion coefficient double than experimental, and
the rdf don't show the two long range peaks, suggesting the lack of
water tetrahedral structure. In the other hand, SPC/E (or even SPC)
shows features very similar to F3C.
In the paper they argue consitency in molecular representation is an
important issue, so if Angle and bond degrees of freedom are allowed
in solute, it must be in water too. So as CHARMM and ENCAD have fairly
the same type of armonic potentials, and in F3C parametrization the
only ENCAD related issues they use were different cutoff methods, F3C
would be independent of ForceField and its implementation would depend
on cutoff or algoritmic issues (as long as the FF would be like AMBER,
CHARMM or ENCAD).
If CHARMM forcefield was parametrized with TIP3P and that is important
to the solute parameters, then may be some problems...but I hope
Brian's research could succeesfully solve them to have a broader
variety of solvents for NAMD/CHARMM use.
Leonardo
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