Multi-scale simulation of proton diffusion in dislocation cores in BaZrO₃

Area of Science:

• Materials Science
• Solid-state Chemistry
• Computational Materials Science

Background:

• Dislocations significantly influence oxide material properties, crucial for electrochemical devices.
• Atomic-level understanding of dislocation effects on ion transport remains limited.
• Proton diffusion in perovskite oxides is key for applications like solid fuel cells.

Purpose of the Study:

• To investigate proton diffusion at dislocations in BaZrO3 using multiscale simulations.
• To elucidate the mechanisms and energy barriers governing proton transport in dislocation cores.
• To compare proton diffusion in dislocation cores versus grain boundaries in Y-doped BaZrO3.

Main Methods:

• Developed a quantum mechanical/molecular mechanical (QM/MM) multiscale simulation program.
• Analyzed proton diffusion properties on 〈100〉 edge dislocations in BaZrO3.
• Calculated migration energy barriers and investigated local lattice deformation and bond order changes.

Main Results:

• Dislocation cores trap protons due to free space and hydrogen bonds, hindering diffusion.
• No evidence of pipeline diffusion was observed; conductivity was decreased, not increased.
• Local lattice deformation and interactions with oxygen and Zr ions control proton transfer energy barriers.

Conclusions:

• Dislocations impede proton diffusion in BaZrO3, reducing ionic conductivity.
• Understanding dislocation-specific proton transport is vital for designing advanced proton conductors.
• This study provides insights into mechanical influences on proton diffusion and guides material preparation.