Predicting two-dimensional carbon phosphide compouds: C2P4 by the global optimization method

Abstract

Using particle swarm optimization (PSO) methodology for crystal structure prediction, we have found two stable two-dimentional (2D) structures of Carbon and Phosphorus compound: C2P4, namely, a-C2P4 (P-42_1m) and b-C2P4 (P-1). Our density functional calculations show that a-C2P4 and b-C2P4 are indirect semiconductors with band gaps of 1.89 (2.76) eV and 1.30 (1.81) eV with GGA-PBE (HSE06), as well as a-C2P4 possesses a band gap larger than 2.0 eV which may create a way for transistors with high on/off scales, optoelectronic devices operating under blue or UV light, and mechanical sensors based on new 2D structures. Furthermore, the effects of tensile strains on electronics properties of two structures have been studied, and the method of strain presents a good way of tuning the gaps of two structures, especially the band gap of a-C2P4 can be linearly tuned larger than 2.0 eV which expands their potential applications in optoelectronics. Finally, two structures are provided with relatively high electron mobility and can be altered from semiconductors to metals by larger tensile strains.