Space formations and nonlinear properties of noncentrosymmetric germanates

Space formations of Ge-O polyhedra have been analyzed for 114 noncentrosymmetric germanates. The type of Ge-O polyhedra space formations is dependent on the stoichiometric ratio SR=n(O)/n(Ge), where n(O) is the number of oxygen and n(Ge) is the number of germanium atoms in formal composition of the compound. Individual (Ge-O) polyhedra are found for SR≥3 chains of the polyhedra that exist in the range of SR=3–5. Only framework formations are possible at SR≤2.7. - graphical abstract: Examples of space formations of polyhedra. - Highlights: • Space formations of Ge-O polyhedra have been analyzed. • The dependence of the type of Ge-O polyhedra space formations on the stoichiometric ratio SR=n(O)/n(Ge) was established. • Set of experimental SHG data of noncentrosymmetric germanates was presented