A valence electron rule for the regular octahedrons of M6 clusters

A valence electron rule is proposed for the stability of the regular octahedrons of the M6 clusters of high-row representative elements in the singlet states. The 6N + 14 (N = 0–2) valence electrons stabilize the Oh geometry. The 6N + 14 valence electron rule is confirmed by the unrestricted density functional theory calculations at the UB3LYP/6-31+G(d) levels.