Non-Crystalline Structures of Ultra-Thin Unsupported Nanowires
  Computer simulations suggest that ultrathin metal wires should develop exotic, non-crystalline stable atomic structures, once their diameter decreases below a critical size of the order of a few atomic spacings. The new structures, whose details depend upon the material and the wire thickness, may be dominated by icosahedral packings. Helical, spiral-structured wires with multi-atom pitches are also predicted. The phenomenon, analogous to the appearance of icosahedral and other non-crystalline shapes in small clusters, can be rationalized in terms of surface energy anisotropy and optimal packing. 
Oguz Gulseren (1, 2, 3 and 4), Furio Ercolessi (2 and 3) and Erio   Tosatti (1, 2 and 3) ((1) International Centre for Theor...