[gmx-users] OPLS united atom

[David van der Spoel]

On Mon, 2002-07-15 at 10:59, Krzysztof Murzyn wrote:
> Hi,
 >
> Thanks for your answer, Erik. Now, having OPLS dihedral parameters
> converted into the Ryckaert-Bellemans form I wonder what happens with 1-4
> interactions. According to the gromacs manual, the use of RB dihedral
> potential implies that all 1-4 interactions are excluded while in the
> united-atom OPLS forcefield two scaling factors  (generate pairs = yes and
> FudgeLJ = 8.0, FudgeQQ = 2.0) are used to include them in the total
> potential.
That only goes for "real" Ryckaert Bellemans. The total potential is
just the sum of dihedral and LJ+Coulomb. In the case of OPLS you
explicitly need the LJ and Coulomb, but with those scaling factors.


> Regards,
> Krzysztof
> 
> 
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-- 
Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel
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