Isostructurality

Isostructurality is the property by which two or more chemical compounds crystallize in the same structure type, such that their crystal structures can be related by a symmetry-preserving transformation. In isostructural families, the atoms occupy analogous positions within the same space group and exhibit similar coordination environments and bond networks, even if the chemical compositions differ.

Determination relies on crystallographic data, typically from X-ray or neutron diffraction. Analysts compare space groups, lattice parameters, and Wyckoff positions, and assess whether a one-to-one correspondence between the atomic networks exists. The lattice parameters may differ in scale, but the topology and connectivity remain the same.

Isostructurality is common in solid-state chemistry and coordination chemistry, where chemical substitutions are made at specific lattice sites without disrupting the overall framework. For example, many ABX3 perovskites form isostructural families when A- and B-site cations are varied, preserving the network of BX6 octahedra. Isostructural relationships are useful for predicting properties and guiding synthesis, as trends in structure often correlate with properties such as electronic structure, ionic conductivity, and hardness.

Limitations include distortions due to size mismatch, temperature, pressure, or strong Jahn–Teller effects, which can lower symmetry or alter connectivity, breaking isostructurality. The terms isostructural and isomorphous are related but not always interchangeable; isostructural emphasizes the same topology, while isomorphous often highlights that compounds belong to a continuous series with similar structure that can be superimposed.