Explaining the entropy forming ability for carbides with the effective atomic size mismatch

Area of Science:

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

Background:

• Multi-principal-element materials offer unique properties.
• The entropy forming ability (EFA) is a common descriptor for predicting single-phase formation.
• Existing methods for predicting phase stability can be computationally intensive.

Purpose of the Study:

• To critically evaluate the EFA descriptor for predicting single-phase formation in complex materials.
• To identify more reliable descriptors for phase stability in solid solutions.
• To explore alternative theoretical frameworks for understanding phase formation in multi-component systems.

Main Methods:

• Investigated the EFA descriptor using atomic relaxations.
• Employed special quasi-random structures (SQS) for modeling.
• Analyzed the correlation between EFA, lattice distortion, and atomic size differences.

Main Results:

• Discovered an inverse correlation between EFA and lattice distortion.
• Demonstrated that large atomic size differences promote multi-phase compounds.
• Showed that small atomic size differences favor single-phase compounds.

Conclusions:

• The EFA parameter is not always a reliable predictor of single-phase formation.
• Atomic size differences are a critical factor in solid solution phase stability.
• Hume-Rothery rules effectively predict phase stability in complex ceramics, offering an alternative to entropy-based approaches.