Silicon rebirth: Ab initio prediction of metallic sp3-hybridized silicon allotropes

We report the prediction of metallic quasione-dimensional sp(3)-hybridized silicon allotropes in the form of prismanes. Silicon prismanes or polysilaprismanes are the silicon nanotubes of a special type constructed from the dehydrogenated molecules of cyclosilanes (silicon rings). By means of density functional theory, the electronic, geometry, energy, and some mechanical properties of these tubes are investigated. Our results show that silicon polyprismanes are thermodynamically stable compounds, and the character of the energy spectrum, as well as the behavior of transmission function near the Fermi level, illustrate that they exhibit non-typical for the silicon systems metallic nature. Moreover, the metallic state of polysilaprismanes is resistant to the mechanical stresses applied along their main axis. Unusual properties predicted in the presented study discover new prospects of application of silicon nanostructures as the basic elements of future micro- and nanoelectronics, as well as in energy, metrology, medical, and information technologies.