Unexpected Semimetallic BiS₂ at High Pressure and High Temperature

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Group V-VI compounds are extensively studied for their diverse properties and applications.
• Diverse stoichiometries can lead to novel compounds with unexpected physicochemical properties.
• Previously, only the A2B3-type stoichiometry was considered energetically stable in this group.

Purpose of the Study:

• To investigate the stability of bismuth trisulfide (Bi2S3) under compression.
• To explore the possibility of new stable stoichiometries in group V-VI compounds.
• To synthesize and characterize novel bismuth-sulfur compounds.

Main Methods:

• High-pressure experiments were employed to study the decomposition of Bi2S3.
• Computational calculations were used to predict stable phases and their properties.
• Synthesis and characterization techniques confirmed the existence of the predicted BiS2 phase.

Main Results:

• Bismuth trisulfide (Bi2S3) was found to be unstable under compression, decomposing into BiS2 and BiS.
• A new, stable bismuth disulfide (BiS2) phase was successfully synthesized.
• The BiS2 phase exhibits semimetallic properties, attributed to an increased sulfur concentration.

Conclusions:

• This study reports the first counterintuitive stable stoichiometry in group V-VI compounds.
• The discovery of BiS2 provides a novel example for designing and synthesizing new materials under pressure.
• The findings challenge existing paradigms regarding stable stoichiometries in this compound class.