BaC: a thermodynamically stable layered superconductor

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Barium-carbon (Ba-C) systems are crucial for understanding material properties.
• Predicting stable phases and their properties under pressure is essential for materials discovery.

Purpose of the Study:

• To comprehensively predict all stable compounds in the Ba-C system.
• To identify novel barium carbide phases and their potential superconducting properties.

Main Methods:

• First-principles variable-composition evolutionary algorithm (USPEX).
• Electron-phonon coupling calculations.
• High-throughput computational screening.

Main Results:

• Barium carbide (BaC2) is metastable across 0-40 GPa.
• Barium carbide (BaC6) is stable from 0-19 GPa.
• A new layered orthorhombic Pbam phase of BaC (stoichiometry Ba2C3) is stable from 3-32 GPa.
• The novel BaC phase exhibits phonon-mediated superconductivity with a critical temperature (Tc) of 4.32 K at 5 GPa.
• This new BaC compound is dynamically stable at 0 GPa.

Conclusions:

• The study reveals new stable phases in the Ba-C system.
• A novel barium carbide phase demonstrates potential for superconductivity at accessible conditions.
• The findings suggest the new BaC compound may be quenchable under normal conditions, opening avenues for experimental investigation.