First-principles study of the structural, electronic and optical properties of two-dimensional PC₆X and PX₆ (X=N, As)

Based on the recently-found bulked graphene-like PC₆ monolayer with a direct band gap of 0.83 eV and an extremely high intrinsic conductivity, we have designed four novel two-dimensional materials, PC₆X and PX₆ (X = N, As). Phonon dispersions showed that these structures are stable except PAs₆. Additionally, the stabilities, electronic structures, effective masses and optical properties of PC₆N, PC₆As and PN₆ were studied by using the method of density-functional theory (DFT) calculations. The calculated band gaps of PC₆N (2.87 eV), PC₆As (2.81 eV) and PN₆ (2.59 eV) have been significantly increased compared with intrinsic PC₆ (0.83 eV). We also explained why band gaps of PC₆N, PC₆As and PN₆ are widened by calculating their partial density of states (PDOS) and Mulliken populations. The obtained effective masses of electrons of PC₆N, PC₆As and PN₆ were compared with that of PC₆. The optical properties of absorption coefficients were shown and analyzed, which indicated that PC₆N and PC₆As are potential high efficiency photocatalysts and appropriate candidates for optoelectronic devices working in blue and ultraviolet region.