Chemically induced graphene to diamond transition: a DFT study

TL;DR

This study uses first-principles calculations to explore how surface-hydrogenated bilayer graphene can spontaneously convert into single-layer diamond with metal atom assistance, enabling pressure-free diamond synthesis.

Contribution

It reveals the mechanism by which metal atoms facilitate graphene-to-diamond transformation at ambient conditions, highlighting the roles of electronic orbitals and atomic size.

Findings

Hf atom significantly lowers formation energy to -5.79 eV.

Metal atoms with empty d orbitals and specific radii promote conversion.

Strong hybridization between carbon p orbitals and metal d orbitals drives the process.

Abstract

The conversion of graphene into diamond is a new way for preparing ultrathin diamond film without pressure. Herein, we investigated the transformation mechanism of surface-hydrogenated bilayer graphene (SHBG) into surface-hydrogenated single-layer diamond (SHSLD) crystal, inserting fifteen kinds of single metal atoms without any pressure, by using the systematical first-principles calculations. Compared with the configuration without metal atom, SHBG can be transformed into SHSLD spontaneously in thermodynamics under the action of single metal atom, and its formation energy can even decrease from 0.82 eV to -5.79 eV under the action of Hf atom. According to our results, the outer electron orbits and atomic radius of metal atom are two important factors that affect the conversion. For the phase transition to occur, the metal atom needs to have enough empty d orbitals, and the radius of the metal atom is in the range of 0.136-0.159 nm. Through further analysis, we find that the p orbitals of carbon atoms and d orbital of metal atom in SHBG will be strongly hybridized, thereby promoting the conversion. The results supply important significance to experimentally prepare diamond without pressure through hydrogenated graphene.