Sandwiched between a set of magnetic phases at lower pressure, and a non magnetic phase at higher pressure, the magnetic state of phase ε{lunate} of oxygen has so far been elusive, together with its crystal structure. Neutron diffraction data indicate an absence of antiferromagnetism, but do not exclude a ferromagnetic order. The recent refinement of the internal atomic positions from single-crystal diffraction finally provides us with a correct structural model to study the possible occurrence of a magnetic ground state. By employing non-collinear spin-polarized density-functional theory we show that the ground state of ε{lunate}-O₂ is non magnetic. We also calculate vibrational spectra and show that ε{lunate}-O₂ possesses an additional vibron mode with large Raman cross section, not seen in experiments yet. © 2008 Elsevier Ltd. All rights reserved.

Anh Pham T., Gebauer R., Scandolo S.

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Từ khóa : Antiferromagnetism; Crystal atomic structure; Crystal structure; Crystals; Diffraction; Ferromagnetism; Ground state; Magnetic materials; Magnetism; Model structures; Molecular crystals; Molecular spectroscopy; Oxygen; Atomic positions; B. High pressure; C. Molecular crystals; Crystal diffractions; D. Magnetism; E. Density functional theory; Ferromagnetic orders; Functional theories; Lower pressures; Magnetic ground states; Magnetic phases; Magnetic states; Neutron diffraction datums; Raman cross sections; Structural models; Density functional theory