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. 2014 Nov 26:4:7194.
doi: 10.1038/srep07194.

Dynamic transition in supercritical iron

Yu D Fomin  1 , V N Ryzhov  1 , E N Tsiok  2 , V V Brazhkin  1 , K Trachenko  3
Affiliations

Dynamic transition in supercritical iron

Yu D Fomin et al. Sci Rep. .

Abstract

Recent advance in understanding the supercritical state posits the existence of a new line above the critical point separating two physically distinct states of matter: rigid liquid and non-rigid gas-like fluid. The location of this line, the Frenkel line, remains unknown for important real systems. Here, we map the Frenkel line on the phase diagram of supercritical iron using molecular dynamics simulations. On the basis of our data, we propose a general recipe to locate the Frenkel line for any system, the recipe that importantly does not involve system-specific detailed calculations and relies on the knowledge of the melting line only. We further discuss the relationship between the Frenkel line and the metal-insulator transition in supercritical liquid metals. Our results enable predicting the state of supercritical iron in several conditions of interest. In particular, we predict that liquid iron in the Jupiter core is in the "rigid liquid" state and is highly conducting. We finally analyse the evolution of iron conductivity in the core of smaller planets such as Earth and Venus as well as exoplanets: as planets cool off, the supercritical core undergoes the transition to the rigid-liquid conducting state at the Frenkel line.

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Figures

Figure 1
Figure 1
(a) Velocity autocorrelation functions for iron at ρ = 10 g/cm3 and different temperatures. The inset enlarges the oscillating part of the plot. (b) Heat capacity of iron at the same density (Color online).
Figure 2
Figure 2. The Frenkel line of iron from two criteria (see the text) in (a) ρ−T and (b) P−T coordinates.
(Color online).
Figure 3
Figure 3. Placing Frenkel line on the phase diagram of iron.
Errors in determination of critical point and metal to insulator transition point are of the order of the symbol size. (Color online).
Figure 4
Figure 4. Diameter of effective hard spheres along the melting line and the Frenkel lines of iron.
(Color online).
Figure 5
Figure 5. Packing fraction of effective hard spheres along the melting and Frenkel lines of iron, along Frenkel line of LJ fluid and along Frenkel line of soft spheres with n = 12.
(Color online).
See this image and copyright information in PMC

References

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