Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ab initio determination on the thermal evolution of the Earth's core   Earth's magnetic field is generated by the liquid outer core and sensitively
depends on the thermal conductivity of the core. The dominant component of the
Earth's core is Fe and Ni. However, current estimates on FeNi mixtures have not
been previously tested at high pressures. In this paper, ab initio simulations
were first applied to calculations of the thermal and electrical conductivities
of FeNi mixtures at Earth's outer core conditions. Compared with the results
for pure Fe, the addition of Ni decreases the thermal conductivity (12.30 W/m/K
on average) along the adiabatic curve in the outer core. Based on the
restriction of the entropy production rate or Joule losses, the existence of Ni
prolongs the age of the inner core. The age of the inner core is 0.66 Ga with
pure Fe and 0.67 Ga with an FeNi mixture when heat flow at the core-mantle
boundary is 12 TW. In contrast, we observe that Ni decreases the thickness of
thermal stratification in the outer core by analyzing the effective temperature
gradient. After inner core solidification, the thickness of thermal
stratification is 417.02 km with pure Fe and 320.12 km with an FeNi mixture
when the cooling rate at the core-mantle boundary is 126 K/Ga.

27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph