  We present results of Brownian dynamics simulations of tethered nanospheres
and tethered nanorods. Immiscibility between tether and nanoparticle
facilitates microphase separation into the bicontinuous, double gyroid
structure (first reported by Iacovella et al. [Phys. Rev. E 75 (2007)] and
Horsch et al. [J. Chem. Phys. 125 (2006)] respectively). We demonstrate the
ability of these nanoparticles to adopt distinct, minimal energy local
packings, in which nanospheres form icosahedral-like clusters and nanorods form
splayed hexagonal bundles. These local structures reduce packing frustration
within the nodes of the double gyroid. We argue that the ability to locally
order into stable structures is key to the formation of the double gyroid phase
in these systems.
