Prussian blue analogues (PBAs) are a broad and important family of microporous inorganic solids, famous for their gas storage (1,2,3,4,5), metal-ion immobilisation (6,7), proton conduction (8,9), and stimuli-dependent magnetic (10, 11, 12), electronic (13) and optical (14) properties. The family also includes the widely-used double-metal cyanide (DMC) catalysts (15,16,17) and the topical hexacyanoferrate/hexacyanomanganate arXiv:1908.10596v1 [cond-mat.mtrl-sci] PBAs is the ability to transport mass reversibly, a process made possible by structural vacancies. Normally presumed random (21,22,23), vacancy arrangements are actually crucially important because they control the connectivity of the micropore network, and hence diffusivity and adsorption profiles (24,25). The long-standing obstacle to characterising PBA vacancy networks has always been the relative inaccessibility of single-crystal samples (26). Here we report the growth of single crystals of a range of PBAs. By measuring and interpreting their X-ray diffuse scattering patterns, we identify for the first time a striking diversity of non-random vacancy arrangements that is hidden from conventional crystallographic analysis of powder samples. Moreover, we show that this unexpected phase complexity can be understood in terms of a remarkably simple microscopic model based on local rules of electroneutrality and centrosymmetry. The hidden phase boundaries that emerge demarcate vacancy-network polymorphs with profoundly different micropore characteristics. Our results establish a clear foundation for correlated defect engineering in PBAs as a means of controlling storage capacity, anisotropy, and transport efficiency.The true crystal structures of PBAs-as of Prussian Blue itself-have long posed a difficult and important problem in solid-state chemistry because their ostensibly simple powder diffraction patterns [ Fig. 1(a)] belie a remarkable complexity at the atomic scale (27,28,29). The common parent structure is based on the cubic lattice and corresponds to the idealised composition M[M (CN) 6 ]. Atoms of type M and M (usually transition-metal cations) occupy alternate lattice vertices and are octahedrally coordinated by bridging cyanide ions (CN − ) at the lattice edges [ Fig. 1(b)]. There is a close conceptual parallel to the double perovskite structure (30); indeed the key considerations of covalency and octahedral coordination geometry that stabilise perovskites amongst oxide ceramics (31) also favour this same architecture for transition-metal cyanides, which accounts for the chemical diversity of PBAs (32). Charge balance

Fermi has discovered two giant gamma-ray-emitting bubbles that extend nearly 10kpc in diameter north and south of the galactic center (GC). The existence of the bubbles was first evidenced in X-rays detected by ROSAT and later WMAP detected an excess of radio signals at the location of the gammaray bubbles. We propose that periodic star capture processes by the galactic supermassive black hole, Sgr A * , with a capture rate 3 × 10 −5 yr −1 and energy release ∼ 3 × 10 52 erg per capture can produce very hot plasma ∼ 10keV with a wind velocity ∼ 10 8 cm/s injected into the halo and heat up the halo gas to ∼ 1keV, which produces thermal X-rays. The periodic injection of hot plasma can produce shocks in the halo and accelerate electrons to ∼TeV, which produce radio emission via synchrotron radiation, and gamma-rays via inverse Compton scattering with the relic and the galactic soft photons.

Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of lightweight, molecule-based magnets by postsynthetic reduction of preassembled coordination networks that incorporate chromium metal ions and pyrazine building blocks. The resulting metal-organic ferrimagnets feature critical temperatures up to 242°C and a 7500-oersted room-temperature coercivity.