Liquid anomalies and Fragility of Supercooled Antimony

TL;DR

This study uses advanced simulations to reveal liquid anomalies and fragility in supercooled antimony, shedding light on its rapid phase change capabilities and structural behavior.

Contribution

It provides the first detailed analysis of liquid and supercooled states of elemental antimony using neural network-based molecular dynamics simulations.

Findings

Identified density maximum and non-monotonic thermodynamic responses.

Introduced a new octahedral order parameter for structural analysis.

Indicated high fragility of antimony as a phase-change material.

Abstract

Phase-change materials (PCMs) based on group IV, V, and VI elements, such as Ge, Sb, and Te, exhibit distinctive liquid-state features, including thermodynamic anomalies and unusual dynamical properties, which are believed to play a key role in their fast and reversible crystallization behavior. Antimony (Sb), a monoatomic PCM with ultrafast switching capabilities, stands out as the only elemental member of this group for which the properties of the liquid and supercooled states have so far remained unknown. In this work, we use large-scale molecular dynamics simulations with a neural network potential trained on first-principles data to investigate the liquid, supercooled, and amorphous phases of Sb across a broad pressure-temperature range. We uncover clear signatures of anomalous behavior, including a density maximum and non-monotonic thermodynamic response functions, and introduce a novel octahedral order parameter that captures the structural evolution of the liquid. Moreover, extrapolation of the viscosity to the glass transition, based on configurational and excess entropies, indicates that Sb is a highly fragile material. Our results present a compelling new case for the connection between the liquid-state properties of phase-change materials and their unique ability to combine high amorphous-phase stability with ultrafast crystallization.