Atoms in Highly Symmetric Environments: H in Rhodium and Cobalt Cages, H in an Octahedral Hole in MgO, and Metal Atoms Ca-Zn in C20 Fullerenes

An atom trapped in a crystal vacancy, metal cage, or fullerene might have many immediate neighbors. Then, the familiar concept of valency even coordination number seems inadequate to describe environment that atom. This difficulty terminology is illustrated here by four systems: H atoms tetragonal-pyramidal rhodium cages, an octahedral cobalt MgO hole, and C20 fullerenes. Density functional theory defines structure energetics for systems. Interactions with its container are characterized quantum molecules (QTAIM) non-covalent interactions (NCI). We establish H2Rh13(CO)243− trianion cannot be considered pentavalent, HCo6(CO)151− anion hexavalent, hexavalent. Instead, one should consider set environmental field defined 5, 6, 6 neighbors; described QTAIM. point further electronic structures QTAIM parameters M@C20, M=Ca Zn. The analysis describes systematic deformation restoration symmetric series.