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 PN(6 )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 op-toelectronic devices working in blue and ultraviolet region.