  In this paper we use computer simulations to examine point defects in systems
of "soft" colloidal particles including Hertzian spheres, and star polymers. We
use Monte Carlo simulations to determine the deformation of the different
crystals associated with vacancies and interstitials and use thermodynamic
integration to predict the equilibrium concentrations of such defects. We find
that the nature of the lattice distortion is mainly determined by the crystal
structure and not by the specifics of the interaction potential. We can
distinguish one-, two-, and three-dimensional lattice distortions and find that
the range of the distortion generally depends on the dimensionality. We find
that in both model systems the deformation of the body-centered cubic (BCC)
crystal caused by an interstitial is one-dimensional and we show that its
structure is well described as a crowdion. Similarly, we show that the
one-dimensional deformation of the hexagonal (H) crystal of Hertzian spheres
caused by a vacancy can be characterized as a voidion. Interestingly, with the
exception of the FCC crystal in the Hertzian sphere model, in all cases we find
that the interstitial concentration is higher than the vacancy concentration.
Most noteworthy, the concentration of interstitials in the BCC crystals can
reach up to 1%.
