Hybrid organic-inorganic perovskites (HOIPs) represent a class of emerging materials with an ABX₃ crystal structure, where A and X are organic cations and halide anions, respectively, while the B-site is typically occupied by metal ions. However, recent advances have led to the development of metal-free perovskites, in which the B-site is occupied by non-metallic species such as NH₄⁺ or K⁺. These compounds exhibit remarkable ferroelectric and piezoelectric properties comparable to traditional oxide perovskites like BaTiO₃, making them promising candidates for next-generation flexible and wearable electronic devices. Among these, MDABCO-NH₄I₃ and MDABCO-KI₃ (MDABCO = N-methyl-N-diazabicyclo[2.2.2]octonium) are isostructural molecular perovskite ferroelectrics that offer a unique platform to investigate how chemical substitution at the B-site influences mechanical behavior.IL-1β Antibody In Vivo
This study systematically investigates the elastic properties and high-pressure responses of MDABCO-NH₄I₃ and MDABCO-KI₃ using first-principles density functional theory (DFT) calculations and in situ high-pressure synchrotron X-ray powder diffraction (HP-PXRD). The results reveal that replacing NH₄⁺ with K⁺ on the B-site leads to substantial enhancements in elastic moduli: Young’s modulus increases by up to 48.1%, shear modulus by 52.4%, and bulk modulus by 56.3%. This dramatic improvement arises from the stronger coordination bonding between K⁺ and I⁻ compared to the hydrogen-bonding network in MDABCO-NH₄I₃. The K–I bonds exhibit shorter bond lengths and higher bond strength, resulting in a more rigid framework that resists deformation under external stress.XRCC1 Antibody site Furthermore, the elastic anisotropy of MDABCO-KI₃ is reduced to less than half that of its NH₄⁺ counterpart, indicating a more uniform mechanical response across different crystallographic directions.
High-pressure experiments confirm these theoretical predictions. While MDABCO-NH₄I₃ begins to amorphize at around 3.2 GPa, MDABCO-KI₃ maintains crystallinity up to 4.5 GPa. The unit cell volume of MDABCO-KI₃ contracts by only 19.PMID:34688744 9% at 8 GPa, compared to 31.2% for MDABCO-NH₄I₃, demonstrating superior resistance to hydrostatic compression. The experimentally derived bulk modulus values (14.12 GPa for MDABCO-KI₃ and 10.14 GPa for MDABCO-NH₄I₃) align well with DFT results, validating the accuracy of the computational model. Structural analysis under pressure shows minimal contraction in K–I bond lengths and K–I–K bond angles, confirming the enhanced rigidity conferred by coordination bonding.
In addition, the acoustic properties of both materials were evaluated. The longitudinal sound velocity (c₃) reaches 2.473 km/s in MDABCO-KI₃—close to the speed of sound in water—suggesting potential applications in underwater acoustic transducers and medical imaging. The specific acoustic impedance (z₃ ≈ 5.7–6.1 MRayl) also shows good matching with water, further supporting their use in biocompatible sonar systems. Poisson’s ratio analyses indicate lower lateral strain in MDABCO-KI₃, consistent with its higher stiffness and brittleness, as confirmed by Pugh’s criterion (K/G < 1.75). These findings demonstrate that elastic properties of molecular perovskite ferroelectrics can be effectively engineered through simple B-site substitution. By replacing NH₄⁺ with K⁺, one achieves a significant increase in mechanical robustness without compromising ferroelectric performance. This work provides a clear pathway for designing mechanically durable molecular ferroelectrics for reliable integration into flexible electronics, sensors, and energy-harvesting devices.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com