Combined First-Principles and Experimental Investigation into the Reactivity of Codeposited Chromium-Carbon under...

Area of Science:

• Materials Science
• High-Pressure Physics
• Computational Materials Science

Background:

• High-pressure synthesis in diamond anvil cells often lacks control over precursor stoichiometry and homogeneity.
• Developing precise synthesis methods is crucial for exploring novel material phases under extreme conditions.

Purpose of the Study:

• To present a novel magnetron cosputtering technique for preparing stoichiometrically precise and atomically mixed amorphous chromium carbide (Cr:C) films.
• To investigate the high-pressure behavior of Cr:C synthesized via this new method and compare experimental findings with theoretical predictions.

Main Methods:

• Magnetron cosputtering was employed to create amorphous Cr:C films with controlled stoichiometry.
• Laser-heated diamond anvil cell experiments were conducted at pressures ranging from 13.5 to 24.3 GPa.
• First-principles calculations were used to investigate the stability of observed chromium carbide phases.

Main Results:

• The synthesis yielded Cr3C (Pnma) across the entire pressure range, consistent with theoretical predictions.
• Two unexpected metastable phases, a novel monoclinic chromium carbide and NaCl-type CrC (Fm3̅m), were discovered.
• First-principles methods revealed a significant stabilizing effect for CrC linked to carbon site substoichiometry.

Conclusions:

• The developed cosputtering method enables precise control over precursor composition for high-pressure synthesis.
• The discovery of unexpected metastable phases underscores the limitations of current crystal structure prediction methods.
• Advanced theoretical approaches are needed to explore complex experimental phase spaces more comprehensively.