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

Abstract

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 ε (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 chemical-bonding character of K from alkaline- to transition-metal. Radioactive decay through the incorporation of 40K into the core could therefore be an important source of energy deep inside the Earth, helping to power the geodynamo and mantle dynamics. Copyright 2003 by the American Geophysical Union.