Strain-driven lone pair electron expression for thermal transport in BiCuSeO.

Area of Science:

• Materials Science
• Solid-State Physics
• Condensed Matter Physics

Background:

• Lone-pair electrons significantly impact lattice anharmonicity and thermal transport in crystals.
• Conventional chemical substitution methods for modulating these properties are discontinuous and irreversible.

Purpose of the Study:

• To introduce a continuous and reversible method for modulating lone-pair electron activity using strain engineering.
• To investigate the effects of strain-induced bond angle distortion on lattice anharmonicity and thermal transport in BiCuSeO.

Main Methods:

• Theoretical modeling of strain effects on BiCuSeO crystal structure and electronic properties.
• Analysis of strain-induced changes in bond angles, electron distribution, and interatomic forces.
• Calculation of phonon band structure, anharmonic phonon-phonon interactions, and Umklapp scattering.

Main Results:

• Tensile strain continuously modulates lone-pair electron distribution and bond overlap.
• Strain intensifies Bi atom anharmonic vibrations and induces reverse O atom vibrations, leading to lattice dynamic disorder.
• A 4% tensile strain reduced the lattice thermal conductivity of BiCuSeO by 54% to 0.53 W/mK at 300 K.

Conclusions:

• Strain engineering provides a robust and continuous method for controlling thermal transport properties.
• The study establishes a multiscale framework linking strain, lone-pair electrons, and phonon dynamics.
• This approach offers a novel strategy for designing materials with tailored thermal conductivity.