Unusually stable helical coil allotrope of phosphorus

TL;DR

This paper predicts a novel helical coil allotrope of phosphorus, which is remarkably stable due to coiling and inter-segment attraction, comparable in stability to black phosphorus, and potentially compatible with carbon nanotubes.

Contribution

It introduces a stable helical coil allotrope of phosphorus, supported by ab initio calculations, with potential applications inside carbon nanotubes.

Findings

Helical coil phosphorus is as stable as black phosphorus.

Coiling adds about 12 meV/atom stabilization energy.

Optimal coil radius is approximately 2.4 nm.

Abstract

We have identified an unusually stable helical coil allotrope of phosphorus. Our ab initio Density Functional Theory calculations indicate that the uncoiled, isolated straight 1D chain is equally stable as a monolayer of black phosphorus dubbed phosphorene. The coiling tendency and the attraction between adjacent coil segments add an extra stabilization energy of about 12 meV/atom to the coil allotrope, similar in value to the approximately 16 meV/atom inter-layer attraction in bulk black phosphorus. Thus, the helical coil structure is essentially as stable as black phosphorus, the most stable phosphorus allotrope known to date. With an optimum radius of 2.4 nm, the helical coil of phosphorus may fit well and even form inside wide carbon nanotubes.