Prediction on a Missing Ferroelectric Butterfly Phosphorus Allotrope and Its Energy-Favorable Low-Dimensional Forms

Elemental phosphorus exhibits a remarkable diversity of allotropes, including black, white, and violet phosphorus, each with unique structural and electronic properties. Recently, phosphorus has experienced a renaissance in scientific interest for its potential applications across various fields. Among these, the red phosphorus (RP) possesses a considerable variety of stacking configurations. By analyzing the preference for the P₂₁ building block in Type II, Type IV, and Type V RP allotropes, we proposed a novel butterfly connected structural scheme. This new structure's stability was well confirmed by <i>ab initio</i> calculations. It is characterized as a semiconductor with a band gap of 1.4 eV, exhibiting a red appearance. Additionally, this structure demonstrates ferroelectric behavior, making it an instance of single-element ferroelectric materials. Furthermore, our investigation of chain-type phosphorus structures within carbon nanotubes (CNTs) revealed that the butterfly type connection scheme represents the lowest energy configuration within specifically sized CNTs.