Internal Mobility, Phase Transitions, and Ionic Conductivity in Na(NH4)6Zr4F23 and Li(NH4)6Zr4F23

The dynamics of fluoride and ammonium ions in Na(NH₄)₆Zr₄F₂₃ (I) and Li(NH₄)₆Zr₄F₂₃ (II) was studied by ¹H and ¹⁹F NMR in the temperature range 170-440 K. Types of ionic motion were determined, and their activation energies were evaluated. In I, phase transitions were found in the temperature ranges 360-370 and 410-415 K. The experimental values of conductivity of Na(NH₄)₆Zr₄F₂₃ and Li(NH₄)₆Zr₄F₂₃ ( 4 × 10^-3 S/cm at T = 420 K) permit one to attribute these fluorides to the class of superionic conductors.     

Ionic Mobility, Phase Transitions, and Electric Conductivity in Ammonium Tetrafluoroantimonate and Heptafluorodiantimonate(III)

The dynamics of the fluoride and proton sublattices and the electrophysical properties of NH₄SbF₄ (I) and NH₄Sb₂F₇ (II) in the temperature range 210-435 K were studied by ¹⁹F and ¹H NMR and impedance spectroscopy. Types of ionic motion were determined and their activation energies were estimated. The structural phase transitions in I and II form the high-temperature modifications -NH₄SbF₄ and -NH₄Sb₂F₇, having high ionic (superionic) conductivity in the range 425-435 K (1.9-1.5×10^-3 S/cm).     

Investigation of Internal Motions in the Fluoride Subsystem and Electric Conductivity in Cesium Heptafluorodiantimonate(III)

The internal mobility of the fluoride ions and the electrophysical characteristics of CsSb₂F₇ were studied by ¹⁹F NMR and impedance spectroscopy in the temperature range 250-480 K. The types of ionic motion in the fluoride subsystem have been determined. A structural phase transition to the -CsSb₂F₇ modification characterized by high ionic (superionic) conductivity above 425 K (1.3× 10^-3 S/cm) has been established.     

Structure and Internal Mobility of Complex Ions in Ammonium Pentafluorotitanate According to XRD and NMR Data

The crystal structure of NH₄TiF₅ (I) was determined (monoclinic crystals, a = 14.683(1), b = 6.392(1), c = 20.821(2) , = 110.538(2); space group P2₁/n, Z = 4). Structure I is built from infinite zigzag chains of TiF₆ octahedra linked by their cis-vertices in the [101] direction; the chains are connected by the ammonium ions forming hydrogen bonds. The chains of octahedra with the surrounding ammonium ions are staggered in the crystal lattice of I. ¹⁹F and ¹H NMR spectroscopy was used to study the dynamics of the complex ions in NH₄TiF₅ in the temperature range 270-530 K. Types of ionic motion in the fluoride and proton subsystems were determined, and activation energies evaluated.     

Crystal Structure of NH4NaTiF6and Internal Mobility of the Complex Anions

Single crystals of NH₄NaTiF₆are studied by X-ray diffraction analysis (automated diffractometer, MoK radiation, graphite monochromator, sin/ 1.0 Å^–1, 1566 reflections with I> 3(I), anisotropic least squares method to R= 0.045 and R _w= 0.040). The compound belongs to the NaRbSnF₆structural type. The types of internal motions of the complex ions NH₄ ⁺and TiF₆ ^2–are determined in the temperature range 200–500 K and compared with the motion of ionic groups in (NH₄)₂TiF₆and Na₂TiF₆crystals.     

New mix-ligand copper(i) and copper(ii) pyrazolate complexes with 2,2′-bipyridine

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Predicting the DNA sequence dependence of nanopore ion current using atomic-resolution Brownian dynamics

It has become possible to distinguish DNA molecules of different nucleotide sequences by measuring ion current passing through a narrow pore containing DNA. To assist experimentalists in interpreting the results of such measurements and to improve the DNA sequence detection method, we have developed a computational approach that has both the atomic-scale accuracy and the computational efficiency required to predict DNA sequence-specific differences in the nanopore ion current. In our Brownian dynamics method, the interaction between the ions and DNA is described by three-dimensional potential of mean force maps determined to a 0.03 nm resolution from all-atom molecular dynamics simulations. While this atomic-resolution Brownian dynamics method produces results with orders of magnitude less computational effort than all-atom molecular dynamics requires, we show here that the ion distributions and ion currents predicted by the two methods agree. Finally, using our Brownian dynamics method, we find that a small change in the sequence of DNA within a pore can cause a large change in the ion current, and validate this result with all-atom molecular dynamics.