[gmx-users] Re: Is there a way to use diffrent scaling factors for 1-4 interaction? (David)

[Xiaobing Feng]

 Thanks David,

    The LJ 1-4 interaction can be modified in [pairs] or [pairtypes] sections.
  I need to use different scaling factors for two 1-4 Coulomb interaction. Can we
  do this using [pairtypes]?  I checked a few force field files, they all used
  two values (c6, c12) or (cs6, cs12), I guess only the LJ 1-4 interaction was
  modified. 
    I managed to convert my force field from DLPOLY to GROMACS. I used nrexcl=2
  to include all 1-4 interaction, also I set gen_pairs=yes, fudgeLJ=-1, fudgeQQ=-0.383
   and in [pairs] I specified a 1-4 atom pairs. This way, two kinds of 1-4 interactions
   can have different scaling factors (one is 1.0, the other is 0.617) for Coulomb 
    interaction. It's not a general way, I don't know how to do it if it needs to 
   use two different Coulomb scaling factors, like 0.6 and 0.8. 

    Thanks very much

        Xiaobing
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Sat, 05 Nov 2005 07:49:15 +0100
> From: David <spoel at xray.bmc.uu.se>
> Subject: Re: [gmx-users] Is there a way to use diffrent scaling
> 	factors for	1-4 interaction?
> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
> Message-ID:
> 	<1131173355.4538.3.camel at 217-208-143-88-o1123.tbon.telia.com>
> Content-Type: text/plain; charset=UTF-8
> 
> On Sat, 2005-11-05 at 13:42 +0800, Xiaobing Feng wrote:
> > Dear gmx-users,
> > 
> >     I'm converting a force field from DLPOLY to GROMACS.
> >   There are two different 1-4 interactions, one has full 1-4 LJ and Coulomb 
> >    interaction, the one has scaling factor 0.0 and 0.617 for 1-4 LJ and Coulomb
> >    interaction, respectively.  Is there a way in GROMACS in which we can
> >     use different scaling factors for different 1-4 interactions?
> By specifying a complete matrix of pairtypes
> 
> > 
> >      Many thanks,
> > 
> >       Xiaobing
> > 
> > 
> > 	
> > 
> > 	



	

	
		
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