Novel superhard carbon: C-centered orthorhombic C8

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Physics

Background:

• The search for novel carbon allotropes with superior mechanical properties is ongoing.
• Understanding the structural and energetic landscape of carbon is crucial for designing new materials.

Purpose of the Study:

• To predict and characterize a new, stable carbon allotrope using advanced computational methods.
• To evaluate the energetic favorability and mechanical properties of the predicted allotrope.

Main Methods:

• Particle-swarm optimization for structural search.
• First-principles calculations to determine energetic and mechanical properties.
• Simulation of X-ray diffraction patterns for comparison with experimental data.

Main Results:

• Prediction of a novel carbon allotrope, C-centered orthorhombic C(8) (Cco-C(8)).
• Cco-C(8) exhibits a 3D sp(3) bonding network, energetically favorable over other known polymorphs up to 100 GPa.
• Simulated properties (X-ray diffraction, density, bulk modulus) match experimental data for recovered superhard carbon.
• Predicted hardness of 95.1 GPa, exceeding that of diamond.

Conclusions:

• Cco-C(8) represents a potentially new, highly stable, and superhard carbon material.
• The findings provide a structural candidate for experimentally observed superhard carbon phases.
• This discovery opens avenues for designing ultra-hard materials based on novel carbon structures.