Giant pressure-induced volume collapse in the pyrite mineral MnS2.
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 (MnS2) undergoes an unprecedented (ΔV ~ 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 ground state 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 dimerization. Our results show how the emergence of metal-metal bonding can stabilize giant spin-lattice coupling in Earth's minerals.
European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex 9, France.
Simon A J
SA
Kimber
Ashkan
A
Salamat
Shaun R
SR
Evans
Harald O
HO
Jeschke
Kaliappan
K
Muthukumar
Milan
M
Tomić
Francesc
F
Salvat-Pujol
Roser
R
Valentí
Maria V
MV
Kaisheva
Ivo
I
Zizak
Tapan
T
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