HR: 0830h
AN: V11D-0525    [PDF]
TI: Understanding Fe-K Alloying at High Pressure Using Density Functional Theory
AU: * Steinle-Neumann, G
EM: g.steinle-neumann@uni-bayreuth.de
AF: University Bayreuth, Bayerisches Geoinstitut, Bayreuth, 95440 Germany
AU: Lee, K K
EM: leeka@uclink.berkeley.edu
AF: University of California, Berkeley, Department of Earth and Planetary Science, Berkeley, CA 94720-4767 United States
AU: Jeanloz, R
EM: jeanloz@uclink.berkeley.edu
AF: University of California, Berkeley, Department of Earth and Planetary Science, Berkeley, CA 94720-4767 United States
AB: Recent experiments in the diamond anvil cell and multianvil apparatus indicate that potassium (K) can be alloyed with iron (Fe) at high pressure which has important implications for the thermal state and history of Earth's interior. Due to the volatility of K, however, the extent of alloying remains unclear in the experiments. Here we investigate by means of first principles calculations the nature and consequences of alloying K into the high pressure polymorph of Fe, hexagonal close packed (hcp), and try to use the results to analyze the experimental data. We perform density functional based computations on hcp Fe supercells of various sizes (32, 48, and 96 atoms) in which K is substituted, using the projector augmented wave method as implemented in VASP. In agreement with experiments we find that substitutional incorporation of K into Fe causes the hcp structure to expand. The atomic size of K in the hcp Fe matrix collapses rapidly as a function of pressure, and is essentially indistinguishable to that of iron at core pressures. We find in agreement with experiments and theory on pure K that at high pressure the bonding character becomes more transition metal like, with electronic d-states of K at the Fermi energy. As magnetism has been found to have a significant effect on computed physical properties of iron up to pressures of 50 GPa we have performed select computations to investigate magnetism. We find magnetism to persist in the bulk of the structure despite the incorporation of the non-magnetic K atom.
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting