Using the DFT PBE0 method, bond indices were calculated and the localization of orbitals in p -, m -, o -clusters of Sb<sub>2</sub>Sn<sub>10</sub> was studied. The K <sub>SnSnSn</sub> indices (0.31-0.41) are larger than the K <sub>SnSbSn</sub> indices (0.28-0.31); I <sub>SnSn </sub>≤ 0.48, I <sub>SbSn </sub>≤ 0.50 and I <sub>SbSb </sub>≤ 0.59. The stability of the cluster with the structure of a distorted icosahedron is ensured by thirteen binding electron pairs that populate 20 orbitals localized near triangular faces. The populations of three-center orbitals vary within 1.91-1.97. Each atom stores an unshared electron pair. The tin valency (2.43-2.57) is greater than the number of valence-active electrons, but less than the coordination number. Antimony valency (2.80-2.81) corresponds to the number of valence-active electrons. Energy increases in the series of p - < m - < o -isomers.
