Superconducting Ce2P3 and CeP2 with an interesting planar P layer

Abstract

The discovery of novel structural units in compounds is of great interest in condensed matter and materials science. This not only leads to interesting properties, especially in superconductivity, as seen in materials like MgB₂, H₃S, and LaH₁₀, but also enhances the understanding of elemental attributes. While various phosphorous (P) structural units have been reported, planar ones remain relatively rare. In this study, based on first-principles calculations, we propose two pressurized compounds: Ce₂P₃ and CeP₂. These compounds exhibit unprecedented planar arrangements, with Ce₂P₃ featuring a dense 3-4-5-polygon arrangement and CeP₂ showcasing a honeycomb structure. This achievement was realized by strategically adjusting the distribution of non-bonding electrons of P atoms. In Ce₂P₃, the P layer consists of two interleaved linear arrays composed of edge-shared irregular triangles, quadrilaterals, and pentagons. More interestingly, CeP₂ retains dynamic stability at ambient pressure, with a superconducting transition temperature (T_c) of 30.77 K. This superconductivity is attributed to the strong interaction between Ce 4f electrons and the phonons of P–P and coupled Ce–P vibrations, and its dynamic stability at ambient pressure is mainly associated with the strong Ce–P interaction. Our work represents a significant step forward in stabilizing metal phosphides with planar P layers.