Unexpected giant negative area compressibility in palladium diselenide

Area of Science:

• Materials Science
• Solid-State Physics
• Mechanics

Background:

• Negative area compressibility (NAC) is a rare phenomenon in solids, exhibiting a 'squeeze-expand' behavior.
• NAC is attractive for pressure-response applications and its coupling with unique physicochemical properties.

Purpose of the Study:

• To report and investigate the negative area compressibility (NAC) behavior in palladium diselenide (PdSe2).
• To elucidate the underlying mechanisms responsible for the giant NAC effect in PdSe2.

Main Methods:

• Experimental synthesis and characterization of palladium diselenide.
• High-pressure studies to observe and quantify NAC behavior.
• Theoretical analysis of structural and electronic changes under pressure.

Main Results:

• Palladium diselenide exhibits a large-magnitude NAC effect over a wide pressure range.
• The NAC behavior is attributed to both layer flattening and anomalous intralayer chemical bond elongation.
• Intralayer-to-interlayer charge transfer and enhanced interlayer interactions drive these structural changes under pressure.

Conclusions:

• The study reveals anomalous intralayer bond elongation as a key contributor to the giant NAC effect in PdSe2.
• This work provides a deeper mechanical understanding of NAC and offers guidelines for exploring new compression-induced properties.