[gmx-users] Twin-range cut-off

Justin A. Lemkul jalemkul at vt.edu
Tue Sep 13 01:25:28 CEST 2011

Rabab Toubar wrote:
> Does anyone has a clear definition or a reference for the Twin-range cut-off? I searched the internet and looked at the manual yet I couldn't get the idea

A twin-range cutoff just means that your short-range cutoffs aren't all the same 
value, such that they form two interaction zones.  Within the shortest, the 
neighbor list is updated every step.  Between the shortest and longest cutoffs, 
the neighbor list is updated every nstlist steps.  For instance:

rlist = 0.9
rcoulomb = 0.9
rvdw = 1.4

are common settings for Gromos96 force fields (in conjunction with PME).  Thus 
there are two interaction zones - the first is if two atoms (or charge groups, 
depending on the algorithm) are within 0.9 nm, and the second is if the two 
interacting species are beyond 0.9 nm but within 1.4 nm of each other.



Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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