Few-Layer PdSe₂ Sheets: Promising Thermoelectric Materials Driven by High Valley Convergence

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Palladium diselenide (PdSe2) is a layered material with potential applications in electronics and thermoelectrics.
• Accurate theoretical prediction of its structural and electronic properties is crucial for material design.
• Existing van der Waals (vdW) correction methods often struggle with layered materials.

Purpose of the Study:

• To benchmark density functional theory (DFT) functionals for predicting the structural and electronic properties of PdSe2.
• To investigate the electronic band structure of monolayer, bilayer, and multilayer PdSe2.
• To explore the potential of PdSe2 for thermoelectric cooling applications.

Main Methods:

• A comprehensive benchmark study using 13 commonly employed DFT functionals.
• Focus on predicting lattice parameters of bulk PdSe2.
• Analysis of electronic band structures for various PdSe2 sheet thicknesses.

Main Results:

• Commonly used vdW-correction methods (DFT-D2, optB88, vdW-DF2) show significant errors (>15%) in lattice parameter prediction.
• PBE-TS series functionals achieve high accuracy (<2% error) for bulk PdSe2 lattice parameters.
• Monolayer PdSe2 exhibits a unique conduction band minimum position, deviating from typical 2D materials.
• High valley convergence observed in conduction and valence bands across different PdSe2 thicknesses.

Conclusions:

• The PBE-TS functionals are recommended for accurate DFT studies of PdSe2.
• The unique electronic structure of PdSe2, particularly the valley convergence, highlights its promise for thermoelectric cooling.
• Further research into the structure-property relationships of pentagonal lattice materials is warranted.