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Updated: Jan 18, 2026

Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
Structural Evidence for the Spin Collapse in High Pressure Solid Oxygen
Federico Aiace Gorelli1, Philip Dalladay-Simpson2, Gaston Garbarino3
1European Laboratory for Non Lnear Spectroscopy (LENS), Istituto Nazionale di Ottica, Center for High Pressure Science and Technology Advanced Research, Shanghai Advanced Research in Physical Sciences (SHARPS), Shanghai, China; , 1690 Cailun Road, Shanghai 201203, China; , Consiglio Nazionale delle Ricerche (CNR-INO), via Nello Carrara 1, 50019 Sesto Fiorentino, Italy; and , via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
None:
Single crystal x-ray diffraction measurements have been carried out on epsilon oxygen up to 30 GPa to examine the behavior of the constituent (O_{2})_{4} units. An isostructural phase transition is evidenced by lattice parameter and intracluster (O_{8}) distance discontinuities and clear changes in the equation of state at 18.1±0.5 GPa on compression. This transition corresponds well to the predicted collapse of the molecular magnetic moment from spin-liquid, ε_{1}, to a spinless, ε_{0}, states of the O_{8} structure. The collapse of the molecular magnetic moment has to date only been supported by spectroscopic data and, until now, has not been substantiated structurally.
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