Basin-Size Mapping: Prediction of Metastable Polymorph Synthesizability Across TaC-TaN Alloys

Area of Science:

• Materials Science
• Computational Materials Science
• Solid State Chemistry

Background:

• Basins of attraction on potential energy surfaces guide experimental synthesis of metastable materials.
• Thermodynamic conditions like composition and pressure influence these basins.
• TaC_1-N alloys are relevant as epitaxial substrates for Al_1-GaN.

Purpose of the Study:

• To computationally investigate how alloying affects basin of attraction sizes in TaC_1-N.
• To predict the potential for nonequilibrium synthesis of metastable TaC_1-N alloys.
• To understand the relationship between structure, energy, and stability in these alloys.

Main Methods:

• Random structure sampling was employed to explore the TaC_1-N phase space.
• Uncertainty quantification using Beta and Dirichlet distributions assessed confidence in results.
• Analysis of polymorph basin sizes and energy distributions was performed.

Main Results:

• A significant composition range favors the rocksalt basin, suggesting potential for nonequilibrium synthesis.
• Metastable rocksalt TaC_1-N alloys are predicted as substrates for Al_1-GaN.
• Higher nitrogen concentrations lead to other metastable polymorphs suitable for III-N growth.
• Basin sizes correlate with energetic preferences for coordination environments.
• Increasing nitrogen content universally shrinks basin sizes, increasing amorphous growth tendency.

Conclusions:

• Nonequilibrium synthesis of metastable rocksalt TaC_1-N alloys is feasible for Al_1-GaN applications.
• Alloying strategies can tune the stability and synthesizability of metastable phases.
• Understanding basin dynamics is crucial for designing novel materials with desired properties.