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First‐principles prediction of fast migration channels of potassium ions in KAlSi 3 O 8 hollandite: Implications for high conductivity anomalies in subduction zones
Author(s) -
He Yu,
Sun Yang,
Lu Xia,
Gao Jian,
Li Hong,
Li Heping
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl069084
Subject(s) - hollandite , ringwoodite , ionic conductivity , conductivity , alkali metal , biogeosciences , geology , ionic bonding , mineralogy , materials science , ion , mantle (geology) , geochemistry , chemistry , electrolyte , earth science , electrode , organic chemistry
Materials sharing the hollandite structure were widely reported as fast ionic conductors. However, the ionic conductivity of KAlSi 3 O 8 hollandite (K‐hollandite), which can be formed during the subduction process, has not been investigated so far. Here first‐principles calculations are used to investigate the potassium ion (K + ) transport properties in K‐hollandite. The calculated K + migration barrier energy is 0.44 eV at a pressure of 10 GPa, an energy quite small to block the K + migration in K‐hollandite channels. The calculated ionic conductivity of K‐hollandite is highly anisotropic and depends on its concentration of K + vacancies. About 6% K + vacancies in K‐hollandite can lead to a higher conductivity compared to the conductivity of hydrated wadsleyite and ringwoodite in the mantle. K + vacancies being commonly found in many K‐hollandite samples with maximum vacancies over 30%, the formation of K‐hollandite during subduction of continental or alkali‐rich oceanic crust can contribute to the high conductivity anomalies observed in subduction zones.