Re: amber-developers: help with 1-4 EEL calculations

From: darden <>
Date: Mon, 12 Sep 2005 09:48:18 -0700

dear guanglei et al
I think i'm the guilty party here. This code change dates from the extra
points additions. That is, we had some issues over what was a 1-4
interaction for extra points. also whether these have dihedrals. so i
separated 1-4s from ephi (also needed to iterate 1-4s for induced dipoles)

If you (guanglei) want to modify things in get_14_cg I can help by
answering questions. it looks like all 1-4 electrostatics are uniformly
scaled but there should be a good alternative for more custom scaling
such as an array of weights---not much of a performance hit
you can e-mail me

On Sun, 11 Sep 2005, Guanglei Cui wrote:

> Hi, all
> I need some help with understanding how the 1-4 EEL calculation is done
> in amber8. I want to increase the scee for certain atom pairs, otherwise
> MD crashes. In the subroutine ephi in ene.f, the comment says "for ewald
> calcs, 1-4 interactions are done in get_14_cg() or get_14_dipole()."
> What does the rest of the ephi() do? It looks to me it does some 1-4 EEL
> calculations. For PME, is the 1-4 EEL calculation done exclusively in
> do_14_cg()?
> Thanks in advance.
> Regards,
> Guanglei
Received on Wed Apr 05 2006 - 23:49:53 PDT
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