At larger sizes the energy to distort becomes larger than the gain in surface energy, and bulk materials (i.e. sufficiently large clusters) generally revert to one of the crystalline close-packing configurations instead. In other words, when icosahedral clusters get sufficiently large, the bulk-atom vote wins out over the surface-atom vote, and the nanoparticles can reduce their energy by converting to a simple single crystal with a Wulff construction shape. This occurs typically in the range where the particles are 10-30 nanometers in diameter, but it does not always happen and the particles can grow to millimeter sizes.
