Local structure of solid and liquid gold probed by reverse Monte Carlo analysis of X-ray absorption data

Area of Science:

• Materials Science
• Computational Physics
• X-ray Spectroscopy

Background:

• Advancements in computational power enable more accurate extended X-ray absorption fine structure (EXAFS) data analysis.
• Existing methods require robust tools for modeling complex atomic structures in condensed and molecular systems.

Purpose of the Study:

• To validate the RMC-GNXAS package for analyzing extended X-ray absorption fine structure (EXAFS) data.
• To study the local structure of solid and liquid gold (Au) using accurate multiple-scattering (MS) simulations.
• To establish a benchmark for analyzing functional materials containing heavy noble atoms.

Main Methods:

• Utilized the RMC-GNXAS package, incorporating the reverse Monte Carlo (RMC) method for structural modeling.
• Employed accurate multiple-scattering (MS) simulations, including relativistic effects, to model EXAFS signals.
• Integrated pair and triplet distribution functions with complementary diffraction data for long-range constraints.

Main Results:

• Successfully reconstructed pair and triplet distribution functions for solid and liquid Au, showing good agreement with literature.
• Demonstrated the significant impact of three-body configurations (MS signals) on solid Au structure at low temperatures.
• Determined the pair distribution function and bond-angle distribution for liquid Au, identifying dominant distorted icosahedral configurations.

Conclusions:

• The RMC-GNXAS approach, including multiple-scattering signals, provides accurate local structure information for condensed matter.
• Solid and liquid gold exhibit distinct structural characteristics, with three-body interactions being critical in the solid phase.
• Liquid gold's atomic configurations align with trends observed in other close-packing liquids, characterized by defective icosahedral structures.