A bond valence sum method to identify potential new fluoride ion conductors

Area of Science:

• Solid-state chemistry
• Materials science
• Computational chemistry

Background:

• The bond valence sum (BVS) method is crucial for studying ionic diffusion in solids.
• Lone-pair cations enhance anionic conductivity but pose challenges for traditional BVS due to irregular coordination.

Purpose of the Study:

• To modify the BVS method to account for lone-pair cations.
• To develop a computational tool for predicting fluoride ion diffusion pathways.
• To identify new fluoride ion conductors.

Main Methods:

• A modified bond valence sum (BVS) approach was developed and implemented as a Python program.
• The method was benchmarked against known fluoride ion conductors and experimental data.
• Screening of fluoride compounds containing lone-pair cations was performed using the Inorganic Crystal Structure Database.

Main Results:

• The modified BVS method successfully predicts preferred F- diffusion pathways.
• Calculated energy barriers correlate with experimentally observed ionic conductivities.
• The F- distribution in β-PbSnF4 was accurately reproduced, validating the method.
• Several novel potential fluoride ion conductors were identified.

Conclusions:

• The modified BVS approach offers a reliable way to study F- diffusion in the presence of lone-pair cations.
• This computational tool can accelerate the discovery of new solid electrolytes for energy applications.