[gmx-users] OPLS 1-4 interactions & intramolecular contributionsto interaction energies ...

[Nagy, Peter I.]

	-----Original Message----- 
	From: gmx-users-bounces at gromacs.org on behalf of Erik Lindahl 
	Sent: Wed 6/23/2004 4:57 AM 
	To: Discussion list for GROMACS users 
	Cc: 
	Subject: Re: [gmx-users] OPLS 1-4 interactions & intramolecular contributionsto interaction energies ...
	
	

	Hi,
	
	> Can anybody tell me what the proper way of including
	> 1-4 non-bonded interactions with the OPLSAA FF is ?
	>> From previous messages in this list I gather that
	> there seems to be no unique definition and the scaling
	> factor for the 1-4 interactions including H-atoms seems
	> to be different in different Gromacs versions. What is
	> this factor in 3.2.1, what is it in 3.1.4 and which is the
	> "correct" one ?
	
	The scaling factors are defined in the force field files and not
	hardcoded. They have always been 0.5 for both charge and LJ in OPLS-AA,
	but other forcefields obviously have different serttings.
	
	For OPLS-AA you should include 1,4 interactions between hydrogen atoms,
	while many other forcefields prescribe you shouldn't (e.g. Gromos96).
	This is controlled with a standard flag to pdb2gmx, but the default
	value is set in the rtp file for the last couple of gromacs versions.
	
	
	Cheers,
	
	Erik
	
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