Tuning the mechanical properties of dicyanamide-based molecular perovskites

ABX(3) molecular perovskites have recently gained attention in the field of ferroelectrics and barocalorics where the materials' mechanical properties such as mechanical stability, compressibility, hardness, and elasticity are important performance criteria. Akin to previous work on ceramic perovskites, research on molecular perovskites benefits from the modular building principle of the perovskite motif, enabling systematic studies to learn about the interplay of chemical composition, structure, and properties. Here we use the molecular perovskite series [(nPr)(3)(CH3)N]M(C2N3)(3) (nPr = -(C3H7) and M = Mn2+, Co2+, Fe2+, Ni2+, Zn2+, Cd2+, Ba2+, Sr2+, Ca2+, Hg2+, or Mg2+) as a model system to study the impact of the M2+ metal species on the mechanical properties via lattice dynamic calculations and high-pressure powder X-ray diffraction. By using the bulk modulus as a proxy, we observe a relationship between geometric factors and mechanical properties that agree with chemical intuition. The results present a step forward for gradually refining our understanding of these materials, and contribute to the long-term goal, the design of materials with targeted macroscopic properties.