Coexistence of pressure-induced structural phases in bulk black phosphorus: a combined x-ray diffraction and Raman study up to 18 GPa

TL;DR

This study investigates pressure-induced structural phase transitions in bulk black phosphorus using x-ray diffraction and Raman spectroscopy, revealing phase coexistence and the influence of experimental conditions up to 18 GPa.

Contribution

It provides a combined analysis of x-ray and Raman data to quantify phase coexistence and highlights the role of non-hydrostatic conditions in Raman spectra of black phosphorus.

Findings

Phase coexistence occurs between ~5 and ~15 GPa.

Non-hydrostatic conditions affect Raman spectral features.

Quantitative data on phase presence aids theoretical modeling.

Abstract

We report a study of the structural phase transitions induced by pressure in bulk black phosphorus by using both synchrotron x-ray diffraction for pressures up to 12.2 GPa and Raman spectroscopy up to 18.2 GPa. Very recently black phosphorus attracted large attention because of the unique properties of fewlayers samples (phosphorene), but some basic questions are still open in the case of the bulk system. As concerning the presence of a Raman spectrum above 10 GPa, which should not be observed in an elemental simple cubic system, we propose a new explanation by attributing a key role to the non-hydrostatic conditions occurring in Raman experiments. Finally, a combined analysis of Raman and XRD data allowed us to obtain quantitative information on presence and extent of coexistences between different structural phases from ~5 up to ~15 GPa. This information can have an important role in theoretical studies on pressure-induced structural and electronic phase transitions in black phosphorus.