High-pressure alloying of potassium and iron: Radioactivity in the Earth’s core?

[1] High-resolution x-ray diffraction provides evidence that potassium (K) alloys with iron (Fe) when the two pure elements are heated together at pressures above 26 gigapascals (GPa). Increases of 2–3% in volume of the e (hexagonal close packed: hcp) high-pressure phase of Fe can be attributed to the incorporation of 1 atomic% ( 7000 ppm by weight) K into Fe. Our results provide experimental support for predictions, derived from quantum mechanical calculations, that pressure can induce the alloying of K with Fe due to a change in the chemicalbonding character of K from alkalineto transition-metal. Radioactive decay through the incorporation of K into the core could therefore be an important source of energy deep inside the Earth, helping to power the geodynamo and mantle dynamics.