Planar vs. three-dimensional X 6 2− , X 2 Y 4 2− , and X 3 Y 3 2− (X, Y = B, Al, Ga) metal clusters: an analysis of their relative energies through the turn-upside-down approach
Despite the fact that B and Al belong to the same group 13 elements, the B
6
2−
cluster prefers the planar
D
2h
geometry, whereas Al
6
2−
favours the
O
h
structure, which is caused by orbital interactions.