  The assembly of colloidal cubic diamond is a challenging process since the
shape and interaction parameters and the thermodynamic conditions where this
structure is stable are elusive. The simultaneous use of shape-anisotropic
particles and strong directional interactions has proven to be a successful
path to exclusively nucleate this structure. Here, using molecular dynamics
simulations, we explore in detail the conditions where nucleation of cubic
diamond from tetrahedral building blocks is favored. In particular, we focus on
the effect of depletion and DNA-mediated interactions to form and stabilize
this cubic diamond crystal. We find that a particular balance between the
strength and range of the depletion interactions enhances the self-assembly of
stable cubic diamond, leading to a narrow region where this structure is
nucleated. Moreover, we determine that stronger short-range depletion
attractions may arrest the system leading to the formation of percolating
diamond networks or fully disordered gel structures. Accordingly, the internal
arrangements of these structures exhibit a distinct variation in terms of
fractal dimension and the presence of six-membered rings that increasingly
acquire internal strain as the arrest gets more pronounced. With these results
we provide a clear route for the self-assembly of cubic colloidal diamond,
towards the realization of crystals with superior photonic properties.
