First-principles study on structural and electronic properties of MPX3 (M = Zn, Cd; X = S, Se) compounds

Metal phosphorous trichalcogenides have been attracting significant scientific interest due to their unique physical properties and promising prospects for device applications. In this work, we perform systematical first-principles calculations to study the structural and electronic properties of MPX3 (M = Zn, Cd; X = S, Se) compounds in C2/m (α-phase) and R3̄ (β-phase) symmetries. The sequence of energetic stabilities of this series of compounds is revealed by total energy calculations, and their dynamical stabilities are confirmed by phonon band spectrum calculations. Electronic band structure calculations show that these MPX3 compounds are all indirect-gap semiconductors, and the bandgaps in sulfides (3.13–3.39 eV) are larger than those in selenides (2.14–2.27 eV). The orbital projected density of states calculations show that the electronic states in these compounds around the Fermi level are all mainly contributed by the p orbitals of chalcogen atoms and phosphorus atoms. Our work has given a systematical understanding of this series of MPX3 compounds, which will provide guidance for future theoretical and experimental studies in related fields.