title: X-ray crystallography, an essential tool for the determination of thermodynamic relationships between crystalline polymorphs.
abstract: After a short review of the controversies surrounding the discovery of crystalline polymorphism in relation to our present day understanding, the methods of how to solve the stability hierarchy of different polymorphs will be briefly discussed. They involve either theoretical calculations, or, more commonly, experimental methods based on classical thermodynamics. The experimental approach is mainly carried out using heat-exchange data associated to the transition of one form into another. It will be demonstrated that work-related data associated to the phase transition should be taken into account and the role of X-ray crystallography therein will be discussed. X-ray crystallography has become increasingly precise and can nowadays provide specific volumes and their differences as a function of temperature, and also as a function of pressure, humidity, and time.
authors.affiliation: Académie nationale de pharmacie, 4, avenue de l'Observatoire, 75270 Paris cedex 06, France.
authors.forename: R
authors.initials: R
authors.lastname: Céolin
authors.affiliation: Caractérisation des matériaux moléculaires à activité thérapeutique (CAMMAT), faculté de pharmacie, université Paris Descartes, 4, avenue de l'Observatoire, case 23, 75270 Paris cedex 06, France. Electronic address: ivo.rietveld@parisdescartes.fr.
authors.forename: I-B
authors.initials: IB
authors.lastname: Rietveld
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods*; D013816:Thermodynamics
keywords: Cristallographie; Crystallography; Diagramme de phases; Phase diagram; Polymorphism; Polymorphisme; Thermodynamics; Thermodynamique