Piezoelectricity in the van der Waals Ferroelectric CuInP2S6 (CIPS): A First-Principles Investigation

CuInP2S6 (CIPS) is one of the few known van der Waals ferroelectrics with a relatively high Curie temperature (Tc = 315 K). This property makes CIPS have a wide range of practical applications, including but not limited to, ferroelectric field-effect transistors, energy-harvesting devices, sensors, and neuromorphic systems. As a material with broken inversion symmetry, CIPS also exhibits piezoelectricity, which has attracted intensive research interest. Here, we perform first-principles calculations to investigate the piezoelectric properties of CIPS. Our results show that the magnitude of its piezoelectric response can vary under different conditions. The theoretical simulations are consistent with recent experimental results and aim to illustrate the underlying physics of the piezoelectric behavior in CIPS.