Raman-scattering study of high-pressure phase transition and amorphization of resorcinol

Abstract

Crystalline resorcinol [C6H4(OH)2] has been shown to amorphize at 40 kbars, solely using Raman scattering. The external modes vanish resulting in a spectrum similar to the density of states spectrum, but the internal modes persist indicating a breakdown of translational and orientational correlation between the molecules. The amorphous state recrystallizes after the pressure is released. We also provide additional information on the known a to P phase transition.

The polymorphic phase transformations in resorcinol at high pressure

“…This fact indicates a start of transition to amorphous phase as it was found in previous experiments [11,12].As the pressure was increased the fraction of amorphous phase increased and at P=17.5 (2) GPa the pure amorphous phase was observed.…”

“…9. The tentative assignment of band frequencies was based on previous Raman spectroscopy data [11,21] and listed in Table 1. For a description of the vibrational modes of the resorcinol molecule we used notations from Ref [21].…”

“…In Raman scattering studies [11] amorphization of resorcinol was reported at P ~ 4 GPa, indicating breakdown of translational and orientational long range correlations between molecules. In contrast, subsequent Raman scattering studies [12] revealed an appearance of the new crystalline  phase of resorcinol at pressures above 5.6 GPa.…”

“…The recent studies of resorcinol [7][8][9][10][11][12] clearly demonstrate that pressure-induced polymorphic phase transitions in resorcinol are quite complex and require further elucidation. Moreover, heating or pressurization rate [12], thermal "history" or purity of the sample strongly affects the sequence of polymorphic phase transitions.…”

Towards an Understanding of the Structurally Based Potential for Mechanically Activated Disordering of Small Molecule Organic Crystals

“…The relatively weak nonbonded intermolecular interactions that comprise small organic molecule crystalline lattices, establishes the potential for partial or complete disordering as the result of grinding. [13][14][15][16][17][18][19] Though frequently observed, the nature of this transition, and the mechanism by which it proceeds is poorly understood. Its relevance to pharmaceutical processing warrants further study, with particular emphasis on characterizing the proclivity that any given organic crystalline material has for this type of transition, based on materials properties that are easily determined by either physical measurement or computational analysis.…”