Electrical Resistivity and Thermodynamic Properties of Iron Under High Pressure

Hieu, Ho Khac; Hai, Tran Thi; Hồng, Nguyễn Thị; Sang, Ngo Dinh; Tuyên, Nguyễn Việt

doi:10.1007/s11664-017-5411-2

Cited by 5 publications

(1 citation statement)

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“…Only a few direct thermal conductivity measurements at high pressure and temperature have been reported (Konôpková et al, 2011(Konôpková et al, , 2016McWilliams et al, 2015). Even though the thermal conductivity can directly be calculated from first-principles calculations (Sha and Cohen, 2011;de Koker et al, 2012;Pozzo et al, 2012Pozzo et al, , 2013Pozzo et al, , 2014Pozzo and Alfè, 2016b;Pourovskii et al, 2017;Xu et al, 2018;Yue and Hu, 2018), the Wiedemann-Franz law has been widely used to estimate the thermal conductivity of the Earth's core from the electrical resistivity measurements (Anderson, 1998;Stacey and Anderson, 2001;Stacey and Loper, 2007;Deng et al, 2013;Gomi et al, 2013Gomi et al, , 2016Seagle et al, 2013;Gomi and Hirose, 2015;Ohta et al, 2016Ohta et al, , 2018Hieu et al, 2017;Suehiro et al, 2017;Pommier, 2018;Silber et al, 2018;Zhang et al, 2018) (see Williams, 2018 for a recent review). The Lorenz number is related to the electronic band structure (Vafayi et al, 2006;Gomi and Hirose, 2015;Secco, 2017).…”

Section: Electronic Specific Heat and Wiedemann-franz Lawmentioning

confidence: 99%

Impurity Resistivity of fcc and hcp Fe-Based Alloys: Thermal Stratification at the Top of the Core of Super-Earths

Gomi

Yoshino

2018

Front. Earth Sci.

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It is widely known that the Earth's Fe dominant core contains a certain amount of light elements such as H, C, N, O, Si, and S. We report the results of first-principles calculations on the band structure and the impurity resistivity of substitutionally disordered hcp and fcc Fe based alloys. The calculation was conducted by using the AkaiKKR (machikaneyama) package, which employed the Korringa-Kohn-Rostoker (KKR) method with the atomic sphere approximation (ASA). The local density approximation (LDA) was adopted for the exchange-correlation potential. The coherent potential approximation (CPA) was used to treat substitutional disorder effect. The impurity resistivity is calculated from the Kubo-Greenwood formula with the vertex correction. In dilute alloys with 1 at. % impurity concentration, calculated impurity resistivities of C, N, O, S are comparable to that of Si. On the other hand, in concentrated alloys up to 30 at. %, Si impurity resistivity is the highest followed by C impurity resistivity. Ni impurity resistivity is the smallest. N, O, and S impurity resistivities lie between Si and Ni. Impurity resistivities of hcp-based alloys show systematically higher values than fcc alloys. We also calculated the electronic specific heat from the density of states (DOS). For pure Fe, the results show the deviation from the Sommerfeld value at high temperature, which is consistent with previous calculation. However, the degree of deviation becomes smaller with increasing impurity concentration. The violation of the Sommerfeld expansion is one of the possible sources of the violation of the Wiedemann-Franz law, but the present results could not resolve the inconsistency between recent electrical resistivity and thermal conductivity measurements. Based on the present thermal conductivity model, we calculated the conductive heat flux at the top of terrestrial cores, which is comparable to the heat flux across the thermal boundary layer at the bottom of the mantle. This indicates that the thermal stratification may develop at the top of the liquid core of super-Earths, and hence, chemical buoyancies associated with the inner core growth and/or precipitations are required to generate the global magnetic field through the geodynamo.

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