Spontaneous graphitization of ultrathin cubic structures: A computational study

TL;DR

This computational study reveals that ultrathin slabs of cubic materials tend to spontaneously convert to layered graphitic structures below a critical thickness, driven by surface energy considerations.

Contribution

It identifies the critical thickness at which cubic structures spontaneously graphitize in ultrathin slabs, expanding understanding of surface-driven phase transitions in materials.

Findings

Ultrathin cubic slabs favor graphitization below a critical thickness.

Surface energy differences drive the spontaneous conversion.

The phenomenon applies to various cubic materials including diamond and boron nitride.

Abstract

Results based on {\em ab initio} density functional calculations indicate a general graphitization tendency in ultrathin slabs of cubic diamond, boron nitride, and many other cubic structures including rocksalt. Whereas such compounds often show an energy preference for cubic rather than layered atomic arrangements in the bulk, the surface energy of layered systems is commonly lower than that of their cubic counterparts. We determine the critical slab thickness for a range of systems, below which a spontaneous conversion from a cubic to a layered graphitic structure occurs, driven by surface energy reduction in surface-dominated structures.