The
metal halide ionic octahedron, [MX6] (M = metal
cation, X = halide anion), is considered to be the fundamental building
block and functional unit of metal halide perovskites. By representing
the metal halide ionic octahedron in halide perovskites as a super
ion/atom, the halide perovskite can be described as an extended ionic
octahedron network (ION) charge balanced by selected cations. This
new perspective of halide perovskites based on ION enables the prediction
of different packing and connectivity of the metal halide octahedra
based on different solid-state lattices. In this work, a new halide
perovskite Cs8Au3.5In1.5Cl23 was discovered on the basis of a BaTiO3-lattice ION {[InCl6][AuCl5][Au/InCl4]3}8–, which is assembled from three different ionic octahedra
[InCl6], [AuCl6], and [Au/InCl6]
and balanced by positively charged Cs cations. The success of this
ION design concept in the discovery of Cs8Au3.5In1.5Cl23 opens up a new venue for the rational
design of new halide perovskite materials.
Emulsions comprising isotropic fluid drops within a nematic host are of interest for applications ranging from biodetection to smart windows, which rely on changes of molecular alignment structures around the drops in response to chemical, thermal, electric, and other stimuli. We show that absorption or desorption of trace amounts of common surfactants can drive continuous transformations of elastic multipoles induced by the droplets within the uniformly aligned nematic host. Out-of-equilibrium dynamics of director structures emerge from a controlled self-assembly or desorption of different surfactants at the drop-nematic interfaces, with ensuing forward and reverse transformations between elastic dipoles, quadrupoles, octupoles, and hexadecapoles. We characterize intertransformations of droplet-induced surface and bulk defects, probe elastic pair interactions, and discuss emergent prospects for fundamental science and applications of the reconfigurable nematic emulsions.
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