High pressure transition in amorphous As(2)S(3) studied by EXAFS

Area of Science:

• Materials Science
• Condensed Matter Physics
• Inorganic Chemistry

Background:

• Vitreous arsenic trisulfide (As2S3) is an important chalcogenide glass with unique optical and electronic properties.
• Understanding its structural behavior under extreme conditions is crucial for its technological applications.

Purpose of the Study:

• To investigate the in situ structural evolution of vitreous As2S3 under high pressure.
• To determine the pressure-induced changes in As-S bonding and coordination.
• To explore the metallization process in As2S3 glass at high pressures.

Main Methods:

• High-pressure experiments utilizing a diamond anvil cell.
• Energy dispersive x-ray absorption spectroscopy (XAS) for structural analysis.
• In situ measurements up to 60 GPa.

Main Results:

• A gradual elongation of the average As-S bond length was observed between 15-50 GPa.
• This bond elongation is attributed to an increase in the coordination number around arsenic atoms.
• A negative shift in the As K absorption edge position indicates progressive metallization of the glass.
• The observed structural changes were found to be reversible upon pressure release.

Conclusions:

• Vitreous As2S3 undergoes significant structural transformations under high pressure, including coordination changes and metallization.
• The reversibility of these changes suggests potential for novel high-pressure material applications.
• High-pressure XAS is a powerful technique for probing the structural dynamics of amorphous materials.