HR: 11:00h
AN: T31G-03 INVITED     [PDF]
TI: Quantum theory and high-pressure experiments on iron-potassium alloying: Radioactivity in the Earth's Core?
AU: * Lee, K K
EM: leeka@uclink.berkeley.edu
AF: Department of Earth & Planetary Science University of California, Berkeley, 307 McCone Hall #4767, Berkeley, CA 94720-4767 United States
AU: Steinle-Neumann, G
EM: G.Steinle-Neumann@uni-bayreuth.de
AF: Bayerisches Geoinstitut Universitat Bayreuth, Universitatsstrasse 30, Bayreuth, D-95447 Germany
AU: Jeanloz, R
EM: jeanloz@uclink.berkeley.edu
AF: Department of Earth & Planetary Science University of California, Berkeley, 307 McCone Hall #4767, Berkeley, CA 94720-4767 United States
AB: Ab-initio quantum mechanical calculations support experimental evidence that several percent potassium (K) can be alloyed into iron (Fe) at high pressure, suggesting that K may have been incorporated into the iron-rich core during and after core segregation. This alloying process is of great importance to the thermal state and history of Earth's deep interior as radioactive decay of $^{40}$K could be an important source of energy for the geodynamo and mantle dynamics. To test the possibility of K subsitution into an $\epsilon$-Fe unit cell, we performed density-functional based ab-initio calculations, with the projector augmented wave method as implemented in the Vienna ab-initio simulation package (VASP), of Fe supercells of various sizes in which K is substituted. In agreement with previous high-pressure diamond-anvil cell experiments we find that substitutional incorporation of K into $\epsilon$-Fe causes the hexagonal close pack (hcp) structure to expand by an amount depending nonlinearly on pressure and concentration, with 3 atomic$%$ substitution causing about 2$%$ volume expansion at 35 GPa. We have used these results to analyze the amount of K that is alloyed into hcp $\epsilon$-Fe found in experiments. Overall, these findings show that it is possible to sequester more than 0.1 atomic$%$ (700 ppm by weight) of K into the Fe-based alloy of the Earth's core, which would provide upwards of 4.5 TW across the core-mantle boundary.
DE: 3924 High-pressure behavior
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8130 Heat generation and transport
DE: 8147 Planetary interiors (5430, 5724)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting