ISSN:
1573-904X
Keywords:
atom-atom potential method
;
polymorphism
;
monotropy
;
sulfanilamide
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Purpose. Sulfanilamide trimorphism was chosen as a model system for comparison between stability hierarchies obtained from lattice-energy calculations with those deduced from the relative locations of the sublimation curves of polymorphs in the sulfanilamide p, T diagram. Methods. The atom-atom potential (AAP) method was used for lattice-energy calculations. The p, T diagram was constructed by using crystallographic and thermodynamic data for α-, β-, and γ- forms, and by assigning the temperatures of the experimentally observed phase transitions to triple points involving the vapour phase. Results. The hierarchy obtained with the AAP method (Eα ≥ Eγ〉〉 Eβ) differs only slightly from that deduced from the positions of the sublimation curves (pγ 〉 pα 〉 pβ) in the p, T diagram at room temperature. No stable phase region was found for form α. Thus it is really monotropic. Conclusions. Provided enthalpy and volume changes at the transitions are accurate enough, it is possible to draw a p, T diagram that accounts for the stability hierarchy of polymorphs.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1016058123659
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