I made this structure during the spring break. Chuang has made a similar structure with several truncated octahedron before. But his structure has three unit cells separated connected. So the first unit cell is not connected to the third unit cell directly. My original goal is to make a structure with six unit cells connected to each other, something like a 2x2x2 cluster. However, the structure seems to be sensitive the small deviation at each local connection. Although truncated octahedron can fill the space. the structure I made seems to have pretty large strain and distorion.