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The metal--cyanide frameworks known as Prussian blue analogues display a suite of diverse and tuneable properties. In particular, they are often highly susceptible to modification by external stimuli,...

Stockholm University invites applications for an assistant professorship and an associate professorship, WISE fellows, within the framework of the Wallenberg Initiative Material Science for Sustainabi

Spin crossover (SCO) is attractive for applications within e.g. sensing or solid-state cooling,but controlling the properties is extremely challenging. Hofmann complexes, with formulaFeLx M(CN)4 ·G (L...

Copper(I) tricyanomethanide, Cu(tcm), is a flexible framework material that exhibits the strongest negative area compressibility (NAC) effect ever observed─a remarkable property with potential applications in pressure sensors, artificial muscles, and shock-absorbing devices. Under increasing pressure, Cu(tcm) undergoes two sequential phase transitions (tetragonal → orthorhombic → monoclinic): It has an initial tetragonal structure (I41md) at ambient conditions, but this structure only persists within a narrow pressure range; at 0.12(3) GPa, a pressure-induced ferroelastic phase transition occurs, transforming Cu(tcm) into a low-symmetry orthorhombic structure (Fdd2). The orthorhombic phase has a NAC of −108(14) TPa–1 in the b–c plane between 0.12(3) and 0.93(8) GPa. The NAC behavior is associated with framework hinge motion in a flexible framework with “wine-rack” topology. At 0.93(8) GPa, Cu(tcm) undergoes a second phase transition and transforms into a layered monoclinic structure (Cc) with topologically interpenetrating honeycomb networks. The monoclinic phase of Cu(tcm) exhibits a slight negative linear compressibility (NLC) of −1.1(1) TPa–1 along the a axis and a zero area compressibility of Kac = Ka + Kc = 0.0(4) TPa–1 in the a–c plane over the pressure range of 0.93–2.63 GPa. In contrast to the orthorhombic phase, its mechanism is understood as the pressure-driven dampening of layer “rippling,” which acts to increase the cross-sectional area of the layer at higher hydrostatic pressures. These findings have implications for understanding the underlying mechanism of NAC phenomenon in framework materials.

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35th European Crystallographic Meeting