Evidence for percolation diffusion of cations and reordering in disordered pyrochlore from accelerated molecular...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Materials Science

Background:

• Cation disorder significantly impacts ionic transport in complex oxides like pyrochlores.
• Understanding cation diffusion mechanisms is crucial for applications in nuclear materials, ceramics, and electronics.
• The relationship between cation disorder and transport properties in pyrochlores remains poorly understood.

Purpose of the Study:

• To investigate the influence of cation disorder on vacancy-mediated cation diffusion in Gd2Ti2O7 pyrochlore.
• To elucidate the dynamic processes governing cation transport under varying disorder levels.
• To explore the role of antisite defects and their network formation in cation diffusivity.

Main Methods:

• Classical and accelerated molecular dynamics simulations were employed.
• Simulations were conducted on the microsecond timescale to capture diffusion events.
• Analysis focused on vacancy-mediated cation diffusion pathways and defect dynamics.

Main Results:

• Cation diffusion is slow at low disorder levels and accelerates with increasing disorder.
• Fast diffusion is facilitated by the formation of an antisite percolation network.
• As the material reorders and antisites annihilate, cation diffusivity decreases, exhibiting non-monotonic behavior.
• The observed relationship between disorder and mass transport differs from other complex oxides.

Conclusions:

• Cation transport in Gd2Ti2O7 pyrochlore is strongly dependent on the degree of cation disorder.
• The formation of an antisite percolation network is a key trigger for rapid cation diffusion.
• The non-monotonic evolution of cation diffusivity with reordering suggests unique transport mechanisms in this material.