Fig. 4. Important structures of β-B from the SSW-NN search. (a) Atomic structure of the most stable configuration, β-II-1, highlighting the location of B16; (b) the key unit in the SK-I framework, highlighting the locations of B13 and the least-coordinated B3; (c) the key unit in the SK-II framework, showing the locations of B17, B18 and the least-coordinated B3; (d) the key unit in the SK-III framework; (e) the locations of B3, B8, B19 and B20; (f) the locations of B8, B10 and B21; (g) the location of B22; (h) the key unit in β-III-18.
