An initio simulations of quantum transport: SI clusters and fullerene chains

The I-V characteristics of small Si_n clusters and short C₂₀ chains between atomistic Al leads were calculated using a new ab initio transport code based on a nonequilibrium Greens function formalism. All of the Si clusters display metallic I-V characteristics, with typical conductances ranging between two and three (units G_o = 2e²/h). The transport properties of these molecular devices may be understood in terms of both the bandstructure of electrodes, and the molecular levels of the clusters as modified by the lead environment. Turning to the shortC₂₀ chains, these behave as short nanowires whose transmission depends sensitively on the orientation and distance between the individual C₂₀ molecules. Transportthrough the molecular chains is accompanied by a significant amount of charge transfer, which however remains localized at the electrode/molecular interface.