Disorder-order structural transformation in electron-poor Sr3Au8Sn3 driven by chemical bonding optimization

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Strontium-gold-tin (Sr3Au8Sn3) is a ternary intermetallic compound.
• Understanding phase transitions in intermetallic compounds is crucial for materials design.

Purpose of the Study:

• To synthesize and characterize Sr3Au8Sn3.
• To investigate the structural phase transition of Sr3Au8Sn3 with varying annealing temperatures.
• To elucidate the driving forces behind the observed structural transformation.

Main Methods:

• Synthesis via fusion of pure metals followed by annealing treatments.
• Single-crystal X-ray diffraction for structural determination.
• Differential thermal analysis (DTA) for transition temperature identification.
• Linear Muffin-Tin Orbital (LMTO-ASA) calculations for electronic structure analysis.

Main Results:

• Sr3Au8Sn3 was synthesized and characterized.
• Two distinct crystal structures were identified: Immm (high-temperature, disordered Au/Sn sites) and Pnnm (low-temperature, ordered Au/Sn sites).
• A structural transition occurs around 454 °C.
• LMTO-ASA calculations indicate the disorder-to-order transformation is driven by optimizing Au-Au and Au-Sn bond populations.

Conclusions:

• Sr3Au8Sn3 exhibits a temperature-dependent structural phase transition.
• The transition involves a change from a disordered to an ordered arrangement of gold and tin atoms.
• Electronic structure calculations confirm that bonding energy optimization drives the phase transition upon cooling.