Layered ferrielectric crystals CuInP2S(Se)6: a study from the first principles

Layered CuInP2S(Se)(6) crystals in ferrielectric and paraelectric phases were investigated for the first time via the plane-wave pseudo-potential methodology within density functional theory (DFT). Was proved that structural and electronic properties of the van der Waals layered crystals should be calculated applying dispersion correction to the DFT formalism. The partial and projected density of states were used to evaluate the electronic band structure changes under phase transition. Instability of the CuInP2S(Se)(6) crystals was successfully explained by the second-order Jahn-Teller effect.