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arXiv · 1305.7119

Giant pressure-induced volume collapse in the pyrite mineral MnS2

Simon A. J. Kimber·Ashkan Salamat·Shaun R. Evans·Harald O. Jeschke·Kaliappan Muthukumar·Milan Tomic·Francesc Salvat-Pujol·Roser Valenti·Maria V. Kaisheva·Ivo Zizak·Tapan Chatterji
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Abstract

Dramatic volume collapses under pressure are fundamental to geochemistry and of increasing importance to fields as diverse as hydrogen storage and high-temperature superconductivity. In transition metal materials, collapses are usually driven by so-called spin-state transitions, the interplay between the single-ion crystal field and the size of the magnetic moment. Here we show that the classical S=5/2 mineral Hauerite undergoes an unprecedented 22 % collapse driven by a conceptually different magnetic mechanism. Using synchrotron x-ray diffraction we show that cold compression induces the formation of a disordered intermediate. However, using an evolutionary algorithm we predict a new structure with edge-sharing chains. This is confirmed as the thermodynamic groundstate using in situ laser heating. We show that magnetism is globally absent in the new phase, as low-spin quantum S=1/2 moments are quenched by dimerisation. Our results show how the emergence of metal-metal bonding can stabilise giant spin-lattice coupling in Earth's minerals.

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Simon A. J. Kimber, Ashkan Salamat, Shaun R. Evans, Harald O. Jeschke, Kaliappan Muthukumar, Milan Tomic, Francesc Salvat-Pujol, Roser Valenti, Maria V. Kaisheva, Ivo Zizak, Tapan Chatterji. 2014-12-23. Giant pressure-induced volume collapse in the pyrite mineral MnS2. https://doi.org/10.1073/pnas.1318543111

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