Isostructural

 ( Crystallography ) 

Isostructural chemical compounds have similar chemical structures. "Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous substances crystallise in the same space group and have the same unit cell dimensions.

Examples include:

• I-Gold(I) bromide is isostructural with gold(I) chloride
• Borazine is isostructural with benzene
• Indium(I) bromide is isostructural with β-thallium(I) iodide and has a distorted rock salt structure.

Many minerals are isostructural when they differ only in the nature of a cation.

Compounds which are isoelectronic usually have similar chemical structures. For example, methane, CH₄, and the ammonium ion, NH₄⁺, are isoelectric and are isostructural as both have a tetrahedral structure. The C-H and N-H bond lengths are different and crystal structures are completely different because the ammonium ion only occurs in salts.