Stress-sign-tunable Poisson's Ratio in Monolayer Blue Phosphorus Oxide

TL;DR

This study demonstrates that the Poisson's ratio of monolayer Blue Phosphorus Oxide can be reversibly tuned from positive to negative by applying strain, revealing strain-dependent deformation mechanisms based on atomic interactions.

Contribution

It introduces a strain-tunable Poisson's ratio in monolayer Blue Phosphorus Oxide, elucidating the underlying deformation mechanisms through first-principles calculations.

Findings

PR switches from positive to negative with strain

Deformation mechanisms involve P-P attraction and P-O repulsion

Strain modulates atomic interaction strengths

Abstract

Negative Poisson's ratio (NPR) materials have attracted tremendous interest due to their unusual physical properties and potential applications. Certain two-dimensional (2D) monolayer materials have also been found to exhibit NPR and the corresponding deformation mechanism varies. In this study, we found, based on first-principles calculations, that the Poisson's ratio (PR) sign of monolayer Blue Phosphorus Oxide (BPO) can be tuned by strain: the PR is positive under uniaxial strain <= -1% but becomes negative under > 0. The deformation mechanism for BPO under strain depends on the mutual competition between the P-P attraction and P-O repulsion effect, and these two factors induce two different deformation pathways (one with positive PR, and the other with NPR). Moreover, with increasing of strain, both the decreased strength of P-P attraction and the increased strength of P-O repulsion effect modulate the PR of BPO from positive to negative.