Electronic and geometric structure of thin stable short silicon nanowires

Using the full-potential linear-muffin-tin-orbital molecular-dynamics method, we have studied the geometric and electronic structures of thin short silicon nanowires consisting of tricapped trigonal prism Si-9 subunits and uncapped trigonal prisms, respectively. Comparing to other possible structures, these structures are found to be the thinnest stable silicon nanowires, being particularly much more stable than the silicon nanotubes built analogously to small carbon nanotubes. As for their electronic structures, these silicon wires show very small gaps of only a few tenths of an eV between the lowest unoccupied energy level and the highest occupied energy level, and the gaps decrease as the stacked layers increase. The results provide guidance to experimental efforts for assembling and growing silicon nanowires.