Structure analysis of liquid bismuth using molecular dynamics simulation

Area of Science:

• Condensed matter physics
• Materials science
• Computational chemistry

Background:

• Liquid bismuth (Bi) displays an unusual local structure not explained by standard models.
• Anomalies include a subpeak in the structure factor and a shoulder in the pair distribution function, linked to Peierls distortion in the A7 crystalline phase.

Purpose of the Study:

• To elucidate the structural origins of anomalies in liquid bismuth.
• To compare the liquid structure with the crystalline A7 structure using advanced simulation techniques.

Main Methods:

• Molecular dynamics (MD) simulations utilizing a machine learning potential.
• Analysis of bond-length and angular-limited triplet distribution functions.
• Polyhedral template matching and angular distribution function analyses.

Main Results:

• MD simulations at 573 K successfully replicated experimental static and dynamic structure factors.
• Anomalous shoulder attributed to a 45° angular correlation forming a minimal cluster (right-angled isosceles triangle).
• Coexistence of minimal clusters and 60° equilateral triangular structures (dense packing) observed, with the latter unique to the liquid phase.

Conclusions:

• Liquid bismuth structure is characterized by a coexistence of minimal clusters (reflecting A7 structure) and dense packing arrangements.
• Distinct angular correlations, specifically 45° and 60°, define the local atomic arrangements.
• Simulation results align with experimental observations, validating the proposed structural model.