Single-Crystal X-ray Diffraction of Wüstite to 30GPa Hydrostatic Pressure
Shu, Jinfu; Mao, Ho-kwang; Hu, Jingzhu; Fei, Yingwei; Hemley, Russell J.
published: May 1, 1998
ArtNo. ESP154017202009, Price: 29.00 €
Phase transition, pressure-volume relations, twinning, and internal strains of a single-crystal wüstite (Fe0.9470) have been studied in a helium pressure medium to 30 GPa with a novel synchrotron X-ray diffraction technique. The long-standing enigma of the high-pressure wüstite has been solved; its crystallographic structure has been proven unequivocally to be rhombohedral. At 18 GPa, the wüstite crystal (cubic) transforms to four twin domains of the rhombohedral phase, with each of the four body diagonals of the original cubic crystal corresponding to a unique c-axis of the rhombohedral phase. Lifting the fourfold degeneracy at the transition causes mismatch at the domain boundaries and produces internal strains. The phase transition is sharp, reversible, and displacive. The P-V relation of the low pressure cubic phase agrees with previous polycrystalline results of Fe0.92O and Fe0.98O wüstites in a neon medium; the P-V relation of the high-pressure rhombohedral phase is reported for the first time.