High-pressure Nucleation of Low-Density Polymorphs*

Chemistry. 2021 Apr 26;27(24):7069-7073. doi: 10.1002/chem.202005121. Epub 2021 Mar 4.

Abstract

New polymorphs β and γ of bis-3-nitrophenyl disulphide, crystallized above 0.3 GPa, are less dense than the ambient-pressure polymorph α. This counterintuitive density relation results from the high-entropy nucleation and subsequent kinetic crystallization. The work performed by pressure compensates the high entropy and temperature product, substantiated in varied conformers and increased chemical potential. Pressure-increased viscosity promotes the kinetic polymorphs, in accordance with empirical Ostwald's rule of stages. It contrasts to mechanochemical techniques, favouring high-density polymorphs.

Keywords: crystal growth; high-pressure chemistry; kinetic crystallization; nucleation; polymorphism.