The Periodate‐Based Double Perovskites M2NaIO6 (M = Ca,Sr, and Ba)

The crystal structures of the M₂NaIO₆ series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I^– with O₂^(air) to I⁷⁺ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali‐metal periodate with the alkaline‐earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P2₁/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba₂NaIO₆ contains the first perfectly octahedral [IO₆]^5– unit reported. The compounds of the ortho‐periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR‐ and Raman‐active vibrations.     

Driving Organic Nanocrystals Dissolution Through Electrochemistry

We have recently discussed how organic nanocrystal dissolution appears in different morphologies and the role of the solution pH in the crystal detriment process. We also highlighted the role of the local molecular chemistry in porphyrin nanocrystals having comparable structures: in water-based acid solutions, protonation of free-base porphyrin molecules is the driving force for crystal dissolution, whereas metal (Zn^II) porphyrin nanocrystals remain unperturbed. However, all porphyrin types, having an electron rich π-structure, can be electrochemically oxidized. In this scenario, a key question is: does electrochemistry represent a viable strategy to drive the dissolution of both free-base and metal porphyrin nanocrystals? In this work, by exploiting electrochemical atomic force microscopy (EC-AFM), we monitor in situ and in real time the dissolution of both free-base and metal porphyrin nanocrystals, as soon as molecules reach the oxidation potential, showing different regimes according to the applied EC potential.     

Renormalization theory in four dimensional scalar fields (II)

We interpret the results of the preceding paper (I) in terms of partial resummations of the perturbative series for the effective interaction. As an application we sketch how our resummation method leads to a simple summation rule leading to a convergent expansion for the Schwinger functions of the planar ₄ ⁴ -theory.     

A coassociativeC *-quantum group with nonintegral dimensions

By weakening the counit and antipode axioms of aC ^*-Hopf algebra and allowing for the coassociative coproduct to be nonunital, we obtain a quantum group, that we call aweak C ^*-Hopf algebra, which is sufficiently general to describe the symmetries of essentially arbitrary fusion rules. This amounts to generalizing the Baaj-Skandalis multiplicative unitaries to multipicative partial isometries. Every finite-dimensional weakC ^*-Hopf algebra has a dual which is again a weakC ^*-Hopf algebra. An explicit example is presented with Lee-Yang fusion rules. We briefly discuss applications to amalgamated crossed products, doubles, and quantum chains.Supported by the Hungarian Scientific Research Fund, OTKA T 016 233.Supported by the Hungarian Scientific Research Fund, OTKA-1815.     

The construction of pointlike localized charged fields from conformal Haag—Kastler nets

Starting from a chiral conformal Haag-Kastler net on two-dimensional Minkowski space we construct associated charged pointlike localized fields which intertwine between arbitrary superselection sectors with finite statistics of the theory. This amounts to a proof of the Spin-Statistics theorem, the PCT theorem and the existence of operator product expansions.This Letter generalizes similar results of a recently published paper by Fredenhagen and the author from the neutral vacuum sector to the the full theory with arbitrary charge and finite statistics.