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Kinetic Control of High-Pressure Solid-State Phase Transitions: A Case Study on L-Serine

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2015
Project Chemical bonding and reactions in molecular crystals at high pressure
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Original article (peer-reviewed)

Journal Journal of Physical Chemistry C
Volume (Issue) 119
Page(s) 18611 - 18617
Title of proceedings Journal of Physical Chemistry C
DOI 10.1021/acs.jpcc.5b05838

Open Access

URL https://boris.unibe.ch/73114/8/Macchi_Manuscript_accepted.pdf
Type of Open Access Repository (Green Open Access)

Abstract

This study demonstrates that the compression rate adds a new perspective to phase diagrams of solids. A particular pressure increase rate may trigger unexpected solid-state transformations, producing otherwise inaccessible phases. Our test case is L-Serine, characterized by a complex high-pressure behavior with three known polymorphs. However, the critical pressure of each transition, the ranges of co-existence of polymorphs, and the existence of an elusive fourth phase remained open questions, here analyzed and solved using synchrotron powder X-ray diffraction at high pressure, under controlled pressure increase rates. Two parallel paths exist and the composition of the system depends on the pressure increase rate and the steps during the compression. A slow and continuous compression favors phase IV, whereas phase II can be observed only with a rapid and sharp compression. No direct inter-conversion occurs between these phases. Moreover, phase III originates only from phase II, but never from phase IV. By controlling the strategy of pressure increase, we obtained a powder of phase IV that enabled solving its unknown structure, which resulted as a distorted superstructure of phase I with a tripled a-axis.
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