A Playground for Heavy Atom Tunnelling: Neutral Substitutional Defect Rearrangement from Diamondoids to Diamonds

Abstract

Many diamond properties are defined by substitutional defects (i. e., a carbon atom replaced by another element), which may involve the formation of structural isomers that can interconvert. Herein, we analysed by computational means the structure, thermodynamics, and kinetics of substitutional nitrogen, boron, and oxygen from small diamondoids up to the diamond bulk, focusing on the possibility of heavy atom quantum tunnelling rearrangement between the isomers. The large range of threshold energies and bond lengths lead to a variety of intriguing behaviours, including cage size dependent thermally activated tunnelling of nitrogen, and quantum delocalization of boron. In addition, we predict that applying an external electric field makes it possible to control the rearrangement thermodynamics and kinetics through tunnelling, which lets us hypothesize that these systems can potentially be used as atomic memory devices.

Quantum tunneling instability of the mythical hexazine and pentazine

“…Nonetheless, it is important to acknowledge that certain molecules, despite being predicted to be minima on the potential energy surface, may be inherently unstable due to quantum tunneling (QT) effects, 15–21 or what we called quantum tunneling instability (QTI). 22,23 Consequently, the decomposition might proceed regardless of the temperature if the reaction complies with specific conditions that enhance the QT process.…”