Application of the phenomenological shell model (PSM) provides an explanation for the enhanced stability of Si12Cr and Si12Fe clusters and relative cluster stability along the Si12M (M=Sc-Ni) series. Sequence of orbital shells in PSM is mostly determined by the confining potential, which depends on the cluster shape. In D-6h hexagonal prism geometry, degenerate 2P and 2D shells undergo splitting, and the energy levels of 2P(z), and 2D(z2) orbitals become higher than those of (2P(x), 2P(y)) and (2D(xy,) 2D(yz), 2D(xz), 2D(x2-y2)), respectively. Therefore, stability of the most stable Si12Cr and Si12Fe clusters is attributed to the filling of the 2S(2)2P(6)2D(8) and 2S(2)2P(6)2D(10) closed shells. (C) 2015 Elsevier B.V. All rights reserved.