Polymorphism of monatomic iodine

doi:10.1103/PhysRevB.111.014103

Polymorphism of monatomic iodine

2025-01-08

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Alexander F. Goncharov *

DOI：10.1103/PhysRevB.111.014103

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We applied synchrotron x-ray diffraction in a diamond-anvil cell at 48-51 GPa, alongside first-principles theoretical calculations, to study the crystal structure of solid atomic iodine at high pressure. We report the synthesis of two phases of atomic iodine at 48-51 GPa via laser heating of iodine (I) in nitrogen (N2) or neon (Ne) media. Unlike the familiar monatomic I4/mmm structure, which consists of crystallographically equivalent atoms, a previously unobserved Pm3n structure determined by single-crystal and powder x-ray diffraction is of an inclusion type, featuring two distinct types of atoms: a central, detached atom and peripheral atoms that form linear chains. Additionally, we observe crystallization of the familiar high-pressure fcc structure, albeit at much lower pressures compared to cold-compressed iodine. The discovery of the Pm3n structure in iodine marks an important step in understanding the pressure-induced phase transition sequence in halogens.

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Polymorphism of monatomic iodine

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