Ivanyukite-Na-T, Na₃[Ti₄(OH)O₃(SiO₄)₃]·7H₂O, ivanyukite-Na-C, Na₂[Ti₄O₂(OH)₂(SiO₄)₃]·6H₂O, ivanyukite-K, K₂[Ti₄(OH)₂O₂(SiO₄)₃]·9H₂O, and ivanyukite-Cu, Cu[Ti₄(OH)₂O₂ (SiO₄)₃]·7H₂O, are new microporous titanosilicates found in a natrolitized microcline-aegirine-sodalite lens in the orthoclase-bearing urtite at the Koashva Mountain (Khibiny Massif, Kola Peninsula, Russia). The minerals occur as well-shaped colorless (ivanyukite-Na-T), pale-orange (ivanyukite-Na-C), pale-blue (ivanyukite-K), and green (ivanyukite-Cu) cubic crystals (up to 1.5 mm in diameter) grown on microcline, vinogradovite, sazykinaite-(Y), natrolite, and djerfisherite. The minerals have vitreous luster and white streak. They are transparent and non-fluorescent. The Mohs hardness is estimated as ~4. The minerals are brittle. Cleavage is perfect on {100} (ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu) or on {101̅1} (ivanyukite-Na-T), fracture is stepped. Density, measured by the sink/float method in heavy liquids, ranges from 2.60 (ivanyukite-Na-C) to 2.70 g/cm³ (ivanyukite-Na-T, ivanyukite-K, and ivanyukite-Cu), whereas calculated densities are: 2.58 (ivanyukite-Na-T), 2.39 (ivanyukite-Na-C), 2.69 (ivanyukite-K), and 2.46 g/cm³ (ivanyukite-Cu). Ivanyukite-Na-T is uniaxial (+), n_ω = 1.76(1), n_ε = 1.85(9) (589 nm), and the other minerals are isotropic, n = 1.73(1). Chemical analysis by electron microprobe gave (wt% for ivanyukite-Na-T, ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu, respectively): Na₂O 7.46, 5.19, 0.27, and 0.17; Al₂O₃ 0.07, 0.21, 0.18, and 0.07; SiO₂ 23.75, 25.47, 23.16, and 24.80; SO₃ 0.00, 0.00, 0.00, and 0.20; K₂O 5.89, 6.34, 7.09, and 6.81; CaO 0.21, 0.14, 0.95, and 0.23; TiO₂ 38.89, 37.81, 36.14, and 38.36; MnO 0.05, 0.33, 0.68, and 0.28; FeO 0.54, 2.17, 0.37, and 0.73; CuO 0.00, 0.00, 2.21, and 6.81; SrO 0.00, 0.00, 0.19, and 0.00; Nb₂O₅ 2.99, 2.90, 3.62, and 3.02; BaO 0.14, 0.00, 0.00, and 0.00; H₂O (by the Penfield method) 19.00, 19.15, 25.00, and 21.50; total 98.99, 99.71, 99.86, and 98.97. The empirical formulae (based on Si+Al = 3 apfu) are (Na_1.82 K_0.95 Ca_0.03 Ba_0.01)_∑2.81[(Ti_3.68Nb_0.17Fe_0.06 Mn_0.01)_∑3.92(Si_2.99 Al_0.01)_∑3.00O_14.59(OH)_1.37]·7.29H₂O (ivanyukite-Na-T), (Na_1.17K_0.94Ca_0.03)_∑2.14[(Ti_3.32Fe_0.21Nb_0.15Mn_0.03)_∑3.71(Si_2.97Al_0.03)_∑3.00 O_12.89(OH)_2.87]·6.01H₂O (ivanyukite-Na-C), (K_1.16Cu_0.21Ca_0.13Na_0.07Sr_0.01)_∑1.58[(Ti_3.49Nb_0.21Mn_0.07Fe_0.04)_∑3.81(Si_2.97Al_0.03)_∑3.00 O_13.19(OH)_2.75]·9.32H₂O (ivanyukite-K), and (Cu_0.62K_0.43Na_0.04Ca_0.03)_∑1.12[(Ti_3.48Nb_0.16Fe_0.07Mn_0.03)_∑3.74(Si_2.99Al_0.01)_∑3.00O_12.88(OH)_2.88(SO₄)_0.02]·7.21H₂O (ivanyukite-Cu). Ivanyukite-Na-T is trigonal, R3m, a = 10.94(2), c = 13.97(4) Å, Z = 3. Other minerals are cubic, P4̅3m a = 7.856(6) (ivanyukite-Na-C), 7.808(2) (ivanyukite-K), and 7.850(7) Å (ivanyukite-Cu); Z = 1. The strongest lines in the powder X-ray diffraction pattern [d_bs(Å) (I_obs) hkl] are: 7.88(100) (011), 3.277(60)(014), 3.175(80)(212), 2.730(50)(220), 2.607(70)(303), 2.471(50)(124), 1.960(60)(044), 1.916(50) (135) (ivanyukite-Na-T); 7.88(100)(100), 4.53(30)(111), 3.205(80)(211), 2.774(30)(220), 2.622(40)(221, 300), 2.478(40)(310), 1.960(30)(400), 1.843(30)(330, 411) (ivanyukite-Na-C); 7.85(100)(100), 3.91(20)(200), 3.201(80) (211), 2.765(20)(220), 2.602(30)(221, 300), 2.471(40)(310), 1.951(30)(400), 1.839(30)(330, 411) (ivanyukite-K); 7.87(100)(100), 3.94(20)(200), 3.205(80)(211), 2.774(20)(220), 2.616(30)(221, 300), 2.481(30)(310), 1.960(30) (400), 1.843(30)(330, 411) (ivanyukite-Cu). The crystal structure of ivanyukite-Na-T [trigonal, R3m, a = 10.921(3), c = 13.885(4) Å, V = 1434.2(7) ų] has been solved from highly mosaic crystal and refined to R₁ = 0.147 on the basis of 723 unique observed reflections. The crystal structures of ivanyukite-group minerals are based upon a 3-dimensional framework of the pharmacosiderite type, consisting of four edge-sharing TiO₆-octahedra interlinked by SiO₄ tetrahedra. The framework has a 3-dimensional system of channels defined by 8-membered rings with an effective channel width of 3.5 Å (calculated as the distance between O atoms across the channels minus 2.7 Å). The channels are occupied by Na⁺ and K⁺ cations and H₂O molecules. The infrared spectra of the ivanyukite group minerals show 14 absorption bands caused by vibrations of Si-O and Ti-O bonds, molecular water, and (OH)⁻ groups. Ivanyukite-Na-T formed as a late-stage, hydrothermal phase of ultra-agpaitic hydrothermalites; ivanyukite-Na-C is produced by partial hydration of ivanyukite-Na-T, and both ivanyukite-K and ivanyukite-Cu are produced by partial hydration of ivanyukite-Na-T and natural cation exchange of Cu for Na near dissolved djerfisherite and chalcopyrite grains. Nomenclature of the ivanyukite group is based on the dominant extraframework cation and symmetry of the crystal structure. The minerals are named in honor of Gregory Yur’evich Ivanyuk, Russian mineralogist and petrologist, head of the Laboratory of Self-Organized Mineral Systems in the Geological Institute of the Kola Science Centre of the Russian Academy of Sciences, for his contributions to the petrology and mineralogy of banded iron-formations, alkaline, and alkaline-ultrabasic massifs.

Electrochemical cells using LiFePO₄ cathode material are considered one of the safest and most resistant to overcharging among Li-ion batteries. However, if LiFePO₄-based electrodes are exposed to high potentials, surface and structural changes may occur in the electrode material. In this study Li/LiFePO₄ half-cells were overcharged under different modes with variable cut-off voltages and charge currents. The change in voltage profile, discharge capacity, surface layers composition, and crystalline structure were characterized after overcharge cycles. It was demonstrated that the cathode material is resistant to short-term overcharging up to 5 V, but undergoes irreversible changes with increasing overcharge time or potential. Thus, despite the well-known tolerance of LiFePO₄-based batteries to overcharge, a long overcharge time or high cut-off voltage leads to destructive changes in the cathode and should be avoided.

The paper presents results of studying the electrochemical properties of poly-3,4-ethylenedioxythiophene films using the methods of cyclic voltammetry and faradaic impedance spectroscopy in...

Azirine-triazole hybrids, 1-R-5-(3-aryl-2H-azirin-2-yl)-1H-1,2,3-triazoles, were selectively synthesized by reaction of 1-(3-aryl-2H-azirin-2-yl)-2-(triphenylphosphoranylidene)ethanones with tosyl and (E)-2-benzoylvinyl azides in high yields at rt. The reaction with 2-azidopyridine makes it possible to obtain azirine-triazole-pyridine hybrids, albeit in moderate yields, at 170 °C. The mechanism and selectivity of the reaction of α-carbonylphosphoranes with azides are discussed on the basis of DFT calculations. According to the calculation, the reaction of α-carbonylphosphoranes with model mesyl azide, leading to 1,5-disubstituted triazoles proceeds via a non-concerted cycloaddition, while the reaction leading to 1,4-disubstituted triazoles proceeds via a concerted azide cycloaddition, but through the transition state which has much higher energy. In contrast to the reaction of α-(triphenylphosphoranylidene)ketones with TsN₃, the reaction with TfN₃ yields the α-diazo ketones. Ni-Catalyzed reaction of azirinyl-1,2,3-triazoles with acetylacetone provides pyrrole-triazole and pyrrole-triazole-pyridine hybrids in good yields under mild conditions.