Anomalous melting behavior under extreme conditions: hard matter turning "soft"

Abstract

We show that a system of particles interacting through the exp-6 pair potential, commonly used to describe effective interatomic forces under high compression, exhibits anomalous melting features such as reentrant melting and a rich solid polymorphism, including a stable BC8 crystal. We relate this behavior to the crossover, with increasing pressure, between two different regimes of local order that are associated with the two repulsive length scales of the potential. Our results provide a unifying picture for the high-pressure melting anomalies observed in many elements and point out that, under extreme conditions, atomic systems may reveal surprising similarities with soft matter.

10 pages, 4 figures

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• The zero-temperature phase diagram of soft-repulsive particle fluids
• Hexatic phase and cluster crystals of two-dimensional GEM4 spheres
• Structural properties of the Jagla fluid
• On the accuracy of the melting curves drawn from modelling a solid as an elastic medium
• Crystalline structures of particles interacting through the harmonic-repulsive pair potential
• Density and structural anomalies in soft-repulsive dimeric fluids
• Reentrant melting of the exp-6 fluid: the role of the repulsion softness
• Structure of the simple harmonic-repulsive system in liquid and glassy states studied by the triple correlation function
• Universal behavior of soft-core fluids near the threshold of thermodynamic stability
• Integral equation study of soft-repulsive dimeric fluids
• Strongly first order melting of a two dimensional molecular solid
• Anomalous behavior and structure of a liquid of particles interacting through the harmonic-repulsive pair potential near the crystallization transition