Postgraduate research study
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PhD project: Alloys in the Earth's core

Project description

We currently understand Earth to be composed of chemically and physically differentiated layers inside: the outermost crust, the mantle, and the core. The core itself is divided on a liquid outer core, and the solid inner core.  While almost 3000 km deep, the core continues to be a key player in the dynamics of Earth at the surface. Indeed, seismic activity in the shape of volcanic eruptions an earthquakes are a direct consequence of an active, hot core and the magnetic field of the Earth, essential to life, is believed to be caused by currents on the liquid outer core. Thus, understanding the physics of deep Earth is fundamental not only to build reliable planetary models, but also to understand our own environment. As depth increases, though, obtaining direct knowledge of the physical and chemical properties of each layer becomes harder and harder, and increasing our understanding relies more and more on indirect seismic wave measurements, diamond anvil cell (DAC) experiments and, recently, computer simulations.

It is known the core is mostly composed of iron, with around 5% nickel, and impurities of light elements such as hydrogen, carbon, and oxygen. However, when performing DAC studies or computational simulations, pure iron is often the composition of choice. This chemical difference could explain part of the discrepancies existing between experiments, theory, and our understanding of Earth's interior. The pressures and temperatures in the core are large enough (roughly 3 million atmospheres and 5000 K) to change dramatically the chemistry of compounds  Recent work shows, for example, that FeO mixtures stabilise in a wide range of stoichiometries at high pressure, not just the expected FeO and Fe2O3.

Under this project, you would analyse the evolution of the stable compositions of the Fe-Ni-O ternary system, at conditions relevant to the Earth's core, using first principles simulations. Eventually, you would establish the compounds' structural, dynamical, and electronic properties. From these, predict observables accessible to laboratory high-pressure experiments and astrophysical measurements. Calculations will, amongst others, utilise national resources such as the ARCHER supercomputer.

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