Universal optical response of Si-Si bonds and its evolution from nanoparticles to bulk crystals

We use quantum-mechanical calculations and classical theories of the optical absorption of free and embedded nanoparticles to demonstrate a universality of the optical response of Si-Si bonds, independent of bonding configurations. We also demonstrate that the classical theory remains valid down to atomic-scale nanoparticles and that the evolution of the optical spectrum of a free nanoparticle would evolve to the bulk spectrum when the particle contains hundreds of thousands of Si atoms.