Structure–Property Relations in Metal-Substituted Polar Chalcogenides under Pressure

Abstract Layered chalcogenides like CuInP2S6 are attracting attention as room-temperature ferroelectrics with enhanced polarization under compression and the ability to undergo pressure-assisted aging. Less has been done to reveal the impact of combined physical and chemical pressure. In this work, we integrate diamond anvil cell techniques with synchrotron-based infrared absorbance and Raman scattering spectroscopies, lattice dynamics calculations, and an analysis of the energy landscape to explore symmetry and space group progressions in the ABP2S6 family of materials (A = Cu, Ag; B = Cr, Sc, V, In). All four of the B-site substituted systems host a common set of pressure-driven structural phase transitions near 4 and 12 GPa that follow trends in metal ion size. Within the Cc space group, smaller cations stabilize new states at significantly lower pressures. For instance, while CuInP2S6 displays a monoclinic Cc → trigonal P31c symmetry restoration across PC,1 = 4.6 GPa, the Sc analog hosts the same progression at 2.6 GPa. We extend these structure–property relations to quaternary systems (many involving magnetic and/or ferroelectric functionality), further supporting the development of pressure-tunable electronic devices for environmental sensing, robotics, health monitoring, and biomachine interfaces.