Phenomenology of polymorphism and topological pressure–temperature diagrams

Abstract

Although polymorphism of drug molecules is often studied with extensive and excellent experimental data, pressure appears to be a forgotten variable. In this article, an analysis is provided of the phase behavior of Atovaquone using available literature data. A pressure- temperature diagram is constructed topologically by way of the Clapeyron equation. The method leads to the conclu- sion that Atovaquone phase I and III behave enantiotropi- cally, like a- and b-sulfur do in their paradigmatic P-T diagram, and that phase I is stable at room temperature and under ''ordinary'' pressure.