Figure 1: Exemplary selected geometric structures of SiN clusters to indicate the prolate growth patter up to the cluster Si30 which is quais-spherical. The reappearing sub-units are highlighted by different colours: distorted octahedron (DO, green), pentagonal bipyramid (PB, blue), triple-cappedtrigonal bipyramid (TTB, brown), double-capped trigonal prism(DTP, yellow), triple-capped trigonal prism (TTP, orange),single-capped square antisprism (SSA, purple) and a double-capped square antiprism (DSA, red). Additionally, reoccurring bowl-shaped Si6 units are circled with a dashed line.