ABSTRACT
INTRODUCTION Whereas polymorphism has been defi ned in other chapters as crystal systems for which a substance can exist in structures characterized by different unit cells, but where each of the forms has exactly the same elemental composition, the term solvatomorphism refers to those systems where the crystal structures of the substance are also defi ned by different unit cells, but where these unit cells differ in their elemental composition through the inclusion of one or molecules of solvent. Another defi nition of a solvatomorph is that it is a crystalline solid in which solvent molecules have become included in the structure through positional substitution at positions that are site-specifi c and that are related to other solvent molecules through translational symmetry.
