Planar Defect Layers Template a High-Pressure InBi Polymorph | JoVE Visualize

Area of Science:

Materials Science
Condensed Matter Physics
Crystallography

Background:

The high-pressure behavior of III-V materials, particularly their order and structure, remains a complex area of research.
Previous studies on Indium-Bismuth (InBi) under high pressure suggested a site-disordered β-Sn structure, which is inconsistent with analogous III-V systems.
Experimental data like X-ray diffraction suggested disorder, but theoretical calculations indicated extremely high temperatures (above 3000 K) were required for such disordering.

Purpose of the Study:

To investigate and propose alternative structural models for Indium-Bismuth (InBi) under high pressure, focusing on planar defects.
To reconcile experimental observations of apparent site disorder with theoretical predictions of high disordering temperatures.
To establish InBi as a model system for understanding unique high-pressure planar defects and their influence on material properties.

Main Methods:

Symmetry analysis of crystallographic transitions to derive potential planar defect structures.
Density Functional Theory (DFT) calculations to investigate the stability and electronic structure of proposed defects.
Comparison of calculated diffraction patterns with experimental data and theoretical disorder barriers.

Main Results:

Identification of two sets of planar defects in InBi that replicate the diffraction signature of a site-disordered β-Sn structure.
These proposed defects are thermodynamically stable under high pressure, supported by DFT calculations showing stabilization with decreasing interlayer separation.
One identified defect structure closely matches the known high-pressure phase of InBi (InBi-ϵ), suggesting defects act as templates for phase growth upon heating.

Conclusions:

The apparent site disorder in InBi under high pressure is likely due to specific planar defects, not a bulk disordered structure.
These defects provide a mechanistic explanation for the observed trends in superconducting critical temperature with increasing pressure.
The methodology for defect identification is generalizable to other materials exhibiting reported high-pressure site disorder.