Pentaheptite diamond: a new carbon allotrope

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• The exploration of novel carbon allotropes beyond diamond is driven by the pursuit of materials with unique and superior properties.
• Understanding sp³-hybridized carbon structures is key to developing advanced materials.

Purpose of the Study:

• To predict and characterize a new sp³-hybridized carbon allotrope.
• To evaluate the stability and properties of the predicted carbon phase.

Main Methods:

• Particle swarm optimization (PSO) for structural prediction.
• First-principles calculations for electronic, phonon, and elastic properties.
• Analysis of total energy, phonon spectra, and elastic constants.

Main Results:

• Prediction of a stable orthorhombic carbon phase, named pentaheptite diamond.
• Confirmation of dynamical, thermal, and mechanical stability at zero pressure.
• Pentaheptite diamond exhibits a high bulk modulus (385 GPa) and Vickers hardness (72.6 GPa), comparable to diamond.
• Calculated direct band gap of 4.18 eV.

Conclusions:

• Pentaheptite diamond is a dynamically, thermally, and mechanically stable carbon allotrope.
• Its properties make it a potential candidate for applications requiring high hardness and specific electronic characteristics.
• This discovery expands the known family of sp³-hybridized carbon materials.