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A wideband near-IR (NIR) luminescence centered at 1080 nm was found in a RbPb(2)Cl(5):Bi single crystal grown by the Bridgman technique. Absorption, luminescence, and excitation of luminescence spectra were investigated at room and cryogenic temperatures. The luminescence was proposed to be due to the (3)P(1)-->(3)P(0) transition in Bi(+) ion.

The discovery of graphene stimulated an intensive search for its analogs and derivatives. One of the most interesting derivatives is hydrographene called graphane. Calculations indicate that bulk graphane is thermodynamically more favorable than all CH hydrocarbons including benzene. At the same time, pressureinduced polymerization of hydrocarbons and their derivatives at room temperature leads to the formation of amorphous products or poorly ordered one-dimensional products such as polyacetylene and benzene-derived carbon nanothreads.Here, we report a high-pressure high-temperature synthesis of several millimetersized samples of bulk graphanes with the composition C-H(D) from benzene and graphene-derivative C-H-N 0.2 from pyridine. X-ray diffraction, transmission electron microscopy, and infrared spectroscopy of new materials reveal relatively large (several nanometers in size) crystalline grains of an sp 3 -bonded graphane lattice (3-cycle-4step, the orthorhombic structure with P bca space-group and parameters a = 9.5-9.8Å, b = 8.9-9.1Å, c = 17.1-17.3Å). The main hydrogen groups in samples are C-H groups connected by aliphatic bonds. The synthesized graphanes at atmospheric pressure are stable up to 500 • C. The macroscopic density of CH samples is 1.5-1.57 g cm −3 and the refractive index is 1.78-1.80. The absorption spectra of samples with a high degree of crystallization exhibits a weak absorption maximum at 2.8 eV, which is responsible for the yellow-orange color, large absorption maximum at 4 eV and an absorption edge associated with the width of the optical gap at 5.2 eV. The bulk modulus (30-37 GPa) and shear modulus (15-18 GPa) of the fabricated samples, as well as their hardness (1-1.5 GPa), are about twice as high as the respective values for polycrystalline graphite. The solution of metalorganic complexes in benzene and pyridine makes it possible to obtain doped graphanes, which can have extraordinary electron transport and magnetic properties.arXiv:1608.07221v1 [cond-mat.mtrl-sci]

"Breathing crystals" based on copper(II) hexafluoroacetylacetonates and pyrazolyl-substituted nitronyl nitroxides comprise the exchange-coupled clusters within the polymeric chains. Owing to an interplay of exchange interaction between copper(II) and nitroxide spins and Jahn-Teller nature of copper(II) complex, the breathing crystals demonstrate thermally and light-induced magnetostructural transitions in many aspects similar to the classical spin crossover. Herewith, we report the first application of variable temperature (VT) far/mid Fourier transform infrared (FTIR) spectroscopy and mid FTIR microscopy to breathing crystals. This VT-FTIR study was aimed toward clarification of the transitions mechanism previously debated on the basis of superconducting quantum interference device, X-ray diffraction, and electron paramagnetic resonance data. VT-FTIR showed the onset of new vibrational bands during phase transitions occurring at the expense of several existing ones, whose intensity was significantly reduced. The most pronounced spectral changes were assigned to corresponding vibrational modes using quantum chemical calculations. A clear-cut correlation was found between temperature-dependent effective magnetic moment of studied compounds and the observed VT-FTIR spectra. Importantly, VT-FTIR confirmed coexistence of two types of copper(II)-nitroxide clusters during gradual magnetostructural transition. Such clusters correspond to weakly coupled and strongly coupled spin states, whose relative contribution depends on temperature. The pronounced difference in the VT-FTIR spectra of two states in breathing crystals is a fingerprint of magnetostructural transition, and understanding of these characteristics achieved by us will be useful for future studies of breathing crystals as well as their diamagnetic analogues.

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Magnetic control of the crystal chirality was announced by Saito et al. [Phys. Rev. Lett. 101, 117402 (2008)] on the ground of experiments in CuB(2)O(4). This claim has raised a sharp dispute in the literature because it seemed to contradict the fundamental symmetry principles. We settle this dispute on the basis of a high-resolution optical spectroscopy study of excitonic transitions in CuB(2)O(4). We find that a large sublattice-sensitive antiferromagnetic linear dichroism (LD) emerges at the Néel temperature T(N)=21  K and show how it could simulate a "magnetic-field control of the crystal chirality." We prove that the discovered LD is related microscopically to the magnetic Davydov splitting. This LD is highly sensitive to subtle changes in the spin subsystems, which allowed us to observe a splitting of the phase transition into an incommensurate magnetic phase into two transitions (T(1)(*)=8.5 and T(2)(*)=7.9  K) and to suggest elliptical spiral structures below T(1)(*), instead of a simple circular helix proposed earlier.