BP_5 Monolayer with Multiferroicity and Negative Poisson's Ratio: A Prediction by Global Optimization Method

TL;DR

This paper predicts a stable, multiferroic BP_5 monolayer with negative Poisson's ratio, high reversible strain, and excellent electronic properties, using a global optimization algorithm, highlighting its potential for advanced nanodevices.

Contribution

It introduces a novel 2D BP_5 phase with unique multiferroic and mechanical properties, predicted through a global optimization method, and explores its potential applications.

Findings

BP_5 monolayer is more stable than graphitic BP.

BP_5 exhibits multiferroicity with large reversible strain.

BP_5 has a negative Poisson's ratio and high carrier mobility.

Abstract

Based on variable components global optimization algorithm, we predict a stable two-dimensional (2D) phase of boron phosphide with 1:5 stoichiometry, i.e. boron pentaphosphide (BP_5) monolayer, which has a lower formation energy than that of the commonly believed graphitic phase (g-BP). BP_5 monolayer is a multiferroic material with coupled ferroelasticity and ferroelectricity. The predicted reversible strain is up to 41.41%, which is the largest among all reported ferroelastic materials. Due to the non-centrosymmetric structure and electronegativity differences between boron and phosphorus atoms, an in-plane spontaneous polarization of 326.0 pC/m occurs in BP_5. Moreover, the recently hunted negative Poisson's ratio property, is also observed in BP_5. As an indirect semiconductor with a band gap of 1.34 eV, BP_5 displays outstanding optical and electronic properties, for instance strongly anisotropic visible-light absorption and high carrier mobility. The rich and extraordinary properties of BP_5 make it a potential nanomaterial for designing electromechanical or optoelectronic devices, such as nonvolatile memory with conveniently readable/writeable capability. Finally, we demonstrate that AlN (010) surface could be a suitable substrate for epitaxy growth of BP_5 monolayer.