  In simple colloidal suspensions, clusters are various multimers that result
from colloid self-association and exist in equilibrium with monomers.There are
two types of potentials that are known to produce clusters: a) potentials that
result from the competition between short-range attraction and long-range
repulsion and are characterized by a global minimum and a repulsive tail and b)
purely repulsive potentials which have a soft shoulder. Using computer
simulations, we demonstrate in this work that potentials with a local minimum
and a repulsive tail, not belonging to either of the known types, are also
capable of generating clusters. A detailed comparative analysis shows that the
new type of cluster-forming potential serves as a bridge between the other two.
The new clusters are expanded in shape and their assembly is driven by entropy,
like in the purely repulsive systems but only at low density. At high density,
clusters are collapsed and stabilized by energy, in common with the systems
with competing attractive and repulsive interactions.
