The 228 valence electron rule for onion-like inorganic fullerenes X1@Y12@Z20 of Ih and Th symmetry

Based on an analysis of the experimentally known 228e- valence electron systems AsNi12As203-, SbNi12Sb203-, SbPd12Sb203-, and SnCu12Sn2012- of Ih symmetry, the new species GeZn12Ge20, KrNi12As20, BrNi12As201-, SeNi12As202-, GeMn12Br20, SeCo12Se206+, and SeFe12Se206- have been designed according to the 228 electron rule introduced in this study for onion-like inorganic fullerenes composed of late main group and transition metal elements. Of these GeZn12Ge20, KrNi12As20, BrNi12As201-, SeNi12As202-, and GeMn12Br20 together with the known AsNi12As203- and its neutral counterpart were investigated at the DFT B3LYP/6-31G(d) level of theory. With one exception they show, in fact, two stable energetic minima of Ih and Th symmetry. Relaxing the symmetry constraints further, e.g. Y12 = {Q6,R6}, additional new neutral species of the general composition Z@Q6R6@Z20 of C5v and C2v symmetry can be formulated, i.e. Z = Se, Q = Fe, R = Mn, following this new building principle, therefore, supporting and inspiring the development of new materials of icosahedral and tetrahedral symmetry. Dedicated to Professor Helmut Schwarz on the occasion of his 80th birthday