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<TITLE>Re: [gmx-users] OPLS 1-4 interactions & intramolecular contributionsto interaction energies ...</TITLE>
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<DIV><FONT size=2>-----Original Message----- <BR><B>From:</B>
gmx-users-bounces@gromacs.org on behalf of Erik Lindahl
<BR><B>Sent:</B> Wed 6/23/2004 4:57 AM <BR><B>To:</B> Discussion list for
GROMACS users <BR><B>Cc:</B> <BR><B>Subject:</B> Re: [gmx-users] OPLS 1-4
interactions & intramolecular contributionsto interaction energies
...<BR><BR></FONT></DIV>
<P><FONT size=2>Hi,<BR><BR>> Can anybody tell me what the proper way of
including<BR>> 1-4 non-bonded interactions with the OPLSAA FF is
?<BR>>> From previous messages in this list I gather that<BR>> there
seems to be no unique definition and the scaling<BR>> factor for the 1-4
interactions including H-atoms seems<BR>> to be different in different
Gromacs versions. What is<BR>> this factor in 3.2.1, what is it in 3.1.4
and which is the<BR>> "correct" one ?<BR><BR>The scaling factors are
defined in the force field files and not<BR>hardcoded. They have always been
0.5 for both charge and LJ in OPLS-AA,<BR>but other forcefields obviously have
different serttings.<BR><BR>For OPLS-AA you should include 1,4 interactions
between hydrogen atoms,<BR>while many other forcefields prescribe you
shouldn't (e.g. Gromos96).<BR>This is controlled with a standard flag to
pdb2gmx, but the default<BR>value is set in the rtp file for the last couple
of gromacs
versions.<BR><BR><BR>Cheers,<BR><BR>Erik<BR><BR>_______________________________________________<BR>gmx-users
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