[gmx-users] How are the clusters of particles created?

[Theodore Si]

Hi all,

In the page 34 of the manual:
The Verlet cut-off scheme is implemented in a very efficient fashion 
based on clusters of particles.
The simplest example is a cluster size of 4 particles. The pair list is 
then constructed based on
cluster pairs.
I want to know on what condition will 4 particles be put in a cluster? 
Can you explain the algorithm in a simple manner?

BR,
Theo