Prediction of a novel monoclinic carbon allotrope

TL;DR

This paper predicts a new monoclinic carbon allotrope, M10-carbon, which is more stable than graphite above 14.4 GPa, has diamond-like hardness, and matches experimental X-ray data.

Contribution

The discovery and characterization of a novel $sp^3$-bonded monoclinic carbon allotrope, M10-carbon, through ab-initio structural search.

Findings

More stable than graphite above 14.4 GPa

Almost as hard as diamond

Matches experimental X-ray diffraction patterns

Abstract

A novel allotrope of carbon with $P2/m$ symmetry was identified during an \emph{ab-initio} minima-hopping structural search which we call $M10$-carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of $sp^3$ bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X-ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite.