A new set of criteria for quantitative analysis of molecular interactions is proposed, which is based on the conceptions of atomic and molecular Voronoi–Dirichlet polyhedra. It is shown that the calculation of solid angles of ligands and complexes as a whole allows one to estimate screening effects and the probability of forming intra- and intercomplex non-valent contacts. The set proposed was used to study the influence of steric factors on the stability of complex groups as well as on the presence or absence of agostic contacts in crystal structures of 808 rare-earth π-complexes.