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arXiv · 1110.2031

Microscopic origins of the anomalous melting behaviour of high-pressure sodium

Hagai Eshet·Rustam Z. Khaliullin·Thomas D. Kühne·Jörg Behler·Michele Parrinello
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Abstract

Recent experiments have shown that sodium, a prototype simple metal at ambient conditions, exhibits unexpected complexity under high pressure. One of the most puzzling phenomena in the behaviour of dense sodium is the pressure-induced drop in its melting temperature, which extends from 1000 K at ~30GPa to as low as room temperature at ~120GPa. Despite significant theoretical effort to understand the anomalous melting its origins have remained unclear. In this work, we reconstruct the sodium phase diagram using an ab-initio-quality neural-network potential. We demonstrate that the reentrant behaviour results from the screening of interionic interactions by conduction electrons, which at high pressure induces a softening in the short-range repulsion. It is expected that such an effect plays an important role in governing the behaviour of a wide range of metals and alloys.

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Hagai Eshet, Rustam Z. Khaliullin, Thomas D. Kühne, Jörg Behler, Michele Parrinello. 2011-10-10. Microscopic origins of the anomalous melting behaviour of high-pressure sodium. https://doi.org/10.1103/physrevlett.108.115701

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