Four superhard carbon allotropes: First-principle study

TL;DR

This study introduces four novel superhard carbon allotropes discovered via a genetic algorithm and first-principles calculations, revealing their stability, semiconducting properties, and exceptional hardness comparable to diamond.

Contribution

The paper reports the prediction and characterization of four new superhard carbon allotropes with unique ring structures using a generalized genetic algorithm and first-principles methods.

Findings

All four allotropes are highly stable compared to recent carbon phases.

Two allotropes are direct-band-gap semiconductors with gaps of 2.261 eV and 4.196 eV.

The other two are indirect-band-gap semiconductors with gaps of 3.105 eV and 3.271 eV.

Abstract

Using a generalized genetic algorithm, we propose four new sp3 carbon allotropes with 5-6-7 (5-6-7-type Z-ACA and Z-CACB) or 4-6-8(4-6-8-type Z4-A3B1 and A4-A2B2) carbon rings. Their stability, mechanical and electronic properties are systematically studied using first-principles method. We find that all these four carbon allotropes show amazing stability in comparison with recently proposed carbon phases. Both ZACA and Z-CACB are direct-band-gap semiconductors with band gaps of 2.261 eV and 4.196 eV, respectively. Whereas Z4-A3B1 and A4-A2B2 are indirect-band-gap semiconductors with band gaps of 3.105 eV and 3.271 eV, respectively. Their mechanical properties reveal that all these four carbon allotropes are superhard materials comparable to diamond.