Re: [AMBER-Developers] About switching function in CHARMM and AMBER

From: Thomas Cheatham <>
Date: Fri, 3 Feb 2017 13:51:16 -0700 (MST)

> I am using CHARMM to do some simulations these days. It seems CHARMM
> like to use CTONnb and CTOFnb these two keywords to define a switching
> function. I found AMBER can also use the switching method (but seems
> only for force, through fswitch keyword). Are the switching method the
> same in CHARMM and AMBER? Thanks!

Yes, and no. CHARMM implements multiple switching functions including
force shift, force switch (I think), energy switch, energy shift (I
think). They like fshift for vdw w/ PME and different "CHARMM" force
fields choose different options. There is a classic paper by Steinbach
and Brooks from mid 90's:

  New spherical-cutoff methods for long-range forces in macromolecular
  Volume 15, Issue 7, July 1994, Pages: 667–683, Peter J. Steinbach and
  Bernard R. Brooks


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Received on Fri Feb 03 2017 - 13:00:03 PST
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