Structure and Bonding in Amorphous Red Phosphorus

TL;DR

This study uses advanced computational methods to elucidate the structure, stability, and bonding in amorphous red phosphorus, revealing its relation to other phosphorus allotropes and providing models for future research.

Contribution

It provides the first detailed first-principles structural models of amorphous red phosphorus, clarifying its stability and bonding characteristics.

Findings

a-P structures have energies slightly higher than phosphorus nanorods

Stability linked to structural relaxation and medium-range order

Quantified covalent and van der Waals interactions in phosphorus phases

Abstract

Amorphous red phosphorus (a-P) is one of the remaining puzzling cases in the structural chemistry of the elements. Here, we elucidate the structure, stability, and chemical bond-ing in a-P from first principles, combining machine-learning and density-functional theo-ry (DFT) methods. We show that a-P structures exist with a range of energies slightly higher than those of phosphorus nanorods, to which they are closely related, and that the stability of a-P is linked to the degree of structural relaxation and medium-range order. We thus complete the stability range of phosphorus allotropes [Angew. Chem. Int. Ed. 2014, 53, 11629] by now including the previously poorly understood amorphous phase, and we quantify the covalent and van der Waals interactions in all main phases of phos-phorus. We also study the electronic densities of states, including those of hydrogenated a-P. Beyond the present study, our structural models are expected to enable wider-ranging first-principles investigations - for example, of a-P-based battery materials.