The structure of a finite particle cluster is typically determined by totalenergy minimization. Here we consider the case where a cluster of soft spheredipoles becomes active, i.e. when the individual particles exhibit anadditional self-propulsion along their dipole moments. We numerically solve theoverdamped equations of motion for soft-sphere dipoles in a solvent. Startingfrom an initial metastable dipolar cluster, the self-propulsion generates acomplex cluster dynamics. The final cluster state has in general a structurewidely different to the initial one, the details depend on the model parametersand on the protocol of how the self-propulsion is turned on. The center-of-massof the cluster moves on a helical path, the details of which are governed bythe initial cluster magnetization. An instantaneous switch to a highself-propulsion leads to fission of the cluster. However, fission does notoccur if the self-propulsion is increased slowly to high strengths. Ourpredictions can be verified through experiments with self-phoretic colloidalJanus-particles and for macroscopic self-propelled dipoles in a highly viscoussolvent.
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