The Orthorhombic Structure of Iron: An in Situ Study at High-Temperature and High-Pressure

An in situ angle-dispersive x-ray diffraction study was undertaken of iron in a laser-heated, diamond-anvil cell up to 2375 kelvin and between 30 and 100 gigapascals in Al2O3- and SiO2-pressure media. The resolution and reliability of diffraction peak in-tensities allow quantitative assessment of a structural model. The results confirm that iron undergoes a phase transformation at high pressures and temperatures. The space group is Pbcm for an orthorhombic lattice, and the atomic topology is close to that of « hexagonal close-packed iron. Iron is the dominant component of Earth’s core, so information on its behav-ior at high pressures and temperatures is necessary to understand the observed seis-mic structure of the core, the chemical and dynamical coupling between the core and the mantle, and Earth’s magnetic field. Iron’s crystallographic structure a