Reorientational Dynamics in Y(BH)·NH ( = 0, 3, and 7): The Impact of NH on BH Dynamics.

The reorientational dynamics of Y(BH)·NH ( = 0, 3, and 7) was studied using quasielastic neutron scattering (QENS) and neutron spin echo (NSE). The results showed that changing the number of NH ligands drastically alters the reorientational mobility of the BH anion. From the QENS experiments, it was determined that the BH anion performs 2-fold reorientations around the C axis in Y(BH), 3-fold reorientations around the C axis in Y(BH)·3NH, and either 2-fold reorientations around the C axis or 3-fold reorientations around the C axis in Y(BH)·7NH.

Promoting Persistent Superionic Conductivity in Sodium Monocarba--dodecaborate NaCBH via Confinement within Nanoporous Silica.

Superionic phases of bulk anhydrous salts based on large cluster-like polyhedral (carba)borate anions are generally stable only well above room temperature, rendering them unsuitable as solid-state electrolytes in energy-storage devices that typically operate at close to room temperature. To unlock their technological potential, strategies are needed to stabilize these superionic properties down to subambient temperatures. One such strategy involves altering the bulk properties by confinement within nanoporous insulators.

Polymorphism of Calcium Decahydrido--decaborate and Characterization of Its Hydrates.

Metal -borates and their derivatives have shown promise in several fields of application from cancer therapy to solid-state electrolytes partly owing to their stability in aqueous solutions and high thermal stability. We report the synthesis and structural analysis of α- and β-CaBH, which are structurally and energetically similar, both showing a tetrahedral coordination of Ca to four -borate cages. The main distinctions between the α- and β-polymorph are found in the crystal system (monoclinic or orthorhombic), topology (wurtzite or ), and the degree of displacement of Ca from the center of the coordination tetrahedron.

Interplay between the Reorientational Dynamics of the BH Anion and the Structure in KBH.

The structure and reorientational dynamics of KBH were studied by using quasielastic and inelastic neutron scattering, Raman spectroscopy, first-principles calculations, differential scanning calorimetry, and synchrotron radiation powder X-ray diffraction. The results reveal the existence of a previously unknown polymorph in between the α'- and β-polymorphs. Furthermore, it was found that the [BH] anion undergoes different reorientational motions in the three polymorphs α, α', and β.

Neutron Scattering Investigations of the Global and Local Structures of Ammine Yttrium Borohydrides.

Complex metal hydrides are a fascinating and continuously expanding class of materials with many properties relevant for solid-state hydrogen and ammonia storage and solid-state electrolytes. The crystal structures are often investigated using powder X-ray diffraction (PXD), which can be ambiguous. Here, we revisit the crystal structure of Y(BD)·3ND with the use of neutron diffraction, which, in comparison to previous PXD studies, provides accurate information about the D positions in the compound.

Structural and Dynamical Properties of Potassium Dodecahydro-monocarba--dodecaborate: KCBH.

MCBH (M: Li, Na) dodecahydro-monocarba--dodecaborate salt compounds are known to have stellar superionic Li and Na conductivities in their high-temperature disordered phases, making them potentially appealing electrolytes in all-solid-state batteries. Nonetheless, it is of keen interest to search for other related materials with similar conductivities while at the same time exhibiting even lower (more device-relevant) disordering temperatures, a key challenge for this class of materials. With this in mind, the unknown structural and dynamical properties of the heavier KCBH congener were investigated in detail by x-ray powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, nuclear magnetic resonance, quasielastic neutron scattering, and AC impedance measurements.

Structural and reorientational dynamics of tetrahydroborate (BH) and tetrahydrofuran (THF) in a Mg(BH)·3THF adduct: neutron-scattering characterization.

Metal borohydrides are considered promising materials for hydrogen storage applications due to their high volumetric and gravimetric hydrogen density. Recently, different Lewis bases have been complexed with Mg(BH4)2 in efforts to improve hydrogenation/dehydrogenation properties. Notably, Mg(BH4)2·xTHF adducts involving tetrahydrofuran (THF; C4H8O) have proven to be especially interesting.

Comparison of anion and cation dynamics in a carbon-substituted -hydroborate salt: H and Na NMR studies of solid-solution Na(CBH)(CBH).

The hexagonal mixed-anion solid solution Na(CBH)(CBH) shows the highest room-temperature ionic conductivity among all known Na-ion conductors. To study the dynamical properties of this compound, we have measured the H and Na nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates in Na(CBH)(CBH) over the temperature range of 80-435 K. It is found that the diffusive motion of Na ions can be described in terms of two jump processes: the fast localized motion within the pairs of tetrahedral interstitial sites of the hexagonal close-packed lattice formed by large anions and the slower jump process via octahedral sites leading to long-range diffusion.

Low-Temperature Rotational Tunneling of Tetrahydroborate Anions in Lithium Benzimidazolate-Borohydride Li(bIm)BH.

To investigate the dynamical properties of the novel hybrid compound, lithium benzimidazolate-borohydride Li(bIm)BH (where bIm denotes a benzimidazolate anion, CNH ), we have used a set of complementary techniques: neutron powder diffraction, ab initio density functional theory calculations, neutron vibrational spectroscopy, nuclear magnetic resonance, neutron spin echo, and quasi-elastic neutron scattering. Our measurements performed over the temperature range from 1.5 to 385 K have revealed the exceptionally fast low-temperature reorientational motion of BH anions.

Tracking the Progression of Anion Reorientational Behavior between -Phase and -Phase Alkali-Metal Silanides, MSiH, by Quasielastic Neutron Scattering.

Quasielastic neutron scattering (QENS) measurements over a wide range of energy resolutions were used to probe the reorientational behavior of the pyramidal SiH anions in the monoalkali silanides (MSiH, where M = K, Rb, and Cs) within the low-temperature ordered -phases, and for CsSiH, the high-temperature disordered -phase and intervening hysteretic transition region. Maximum jump frequencies of the -phase anions near the - transitions range from around 10 s for -KSiH to 10 s and higher for -RbSiH and -CsSiH. The -phase anions undergo uniaxial 3-fold rotational jumps around the anion quasi- symmetry axis.

Glassy carbon, NIST Standard Reference Material (SRM 3600): hydrogen content, neutron vibrational density of states and heat capacity.

Commercial glassy carbon plates being used as absolute intensity calibration standards in small-angle X-ray scattering applications (NIST SRM 3600) have been characterized in several recent publications. This contribution adds to the characterization by measuring the hydrogen content of a plate to be (4.8 ± 0.

Latent Porosity in Alkali-Metal MBF Salts: Structures and Rapid Room-Temperature Hydration/Dehydration Cycles.

Structures of the alkali-metal hydrates Li(HO)Z, LiK(HO)Z, Na(HO)Z, and Rb(HO)Z, unit cell parameters for RbZ and Rb(HO)Z, and the density functional theory (DFT)-optimized structures of KZ, K(HO)Z, RbZ, Rb(HO)Z, CsZ, and Cs(HO)Z are reported (Z = BF) and compared with previously reported X-ray structures of Na(HO)Z, K(HO)Z, and Cs(HO)Z. Unusually rapid room-temperature hydration/dehydration cycles of several MZ/M(HO)Z salt hydrate pairs, which were studied by isothermal gravimetry, are also reported. Finely ground samples of KZ, RbZ, and CsZ, which are not microporous, exhibited latent porosity by undergoing hydration at 24-25 °C in the presence of 18 Torr of HO(g) to K(HO)Z, Rb(HO)Z, and Cs(HO)Z in 18, 40, and 16 min, respectively.

Comparison of the Coordination of BF, BCl, and BH to Na in the Solid State: Crystal Structures and Thermal Behavior of Na(BF), Na(HO)(BF), Na(BCl), and Na(HO)(BCl).

The synthesis of high-purity NaBF and the crystal structures of Na(BF) (5 K neutron powder diffraction (NPD)), Na(HO)(BF) (120 K single-crystal X-ray diffraction (SC-XRD)), Na(BCl) (5 and 295 K NPD), and Na(HO)(BCl) (100 K SC-XRD) are reported. The compound Na(HO)(BF) contains {[(Na(μ-HO)Na(μ-HO))]} infinite chains; the compound Na(HO)(BCl) contains discrete [(HO)Na(μ-HO)Na(HO)] cations with OH···O hydrogen bonds linking the terminal HO ligands. The structures of the two hydrates and the previously published structure of Na(HO)(BH) are analyzed with respect to the relative coordinating ability of BF, BH, and BCl toward Na ions in the solid state (i.

Structure-dependent vibrational dynamics of Mg(BH) polymorphs probed with neutron vibrational spectroscopy and first-principles calculations.

The structure-dependent vibrational properties of different Mg(BH) polymorphs (α, β, γ, and δ phases) were investigated with a combination of neutron vibrational spectroscopy (NVS) measurements and density functional theory (DFT) calculations, with emphasis placed on the effects of the local structure and orientation of the BH anions. DFT simulations closely match the neutron vibrational spectra. The main bands in the low-energy region (20-80 meV) are associated with the BH librational modes.

Unparalleled Lithium and Sodium Superionic Conduction in Solid Electrolytes with Large Monovalent Cage-like Anions.

Solid electrolytes with sufficiently high conductivities and stabilities are the elusive answer to the inherent shortcomings of organic liquid electrolytes prevalent in today's rechargeable batteries. We recently revealed a novel fast-ion-conducting sodium salt, NaBH, which contains large, icosahedral, divalent BH anions that enable impressive superionic conductivity, albeit only above its 529 K phase transition. Its lithium congener, LiBH, possesses an even more technologically prohibitive transition temperature above 600 K.

Fast lithium-ionic conduction in a new complex hydride-sulphide crystalline phase.

A new crystalline phase derived from a 90LiBH4:10P2S5 mixture displays high lithium-ionic conductivity of log(σ/S cm(-1)) = -3.0 at 300 K. It is stable up to 473 K and has both a wide potential window of 0-5 V and favorable mechanical properties for battery assembly.

Exceptional superionic conductivity in disordered sodium decahydro-closo-decaborate.

Na2 B10 H10 exhibits exceptional superionic conductivity above ca. 360 K (e.g.

Sodium superionic conduction in Na2B12H12.

Impedance measurements indicate that Na2B12H12 exhibits dramatic Na(+) conductivity (on the order of 0.1 S cm(-1)) above its order-disorder phase-transition at ≈529 K, rivaling that of current, solid-state, ceramic-based, Na-battery electrolytes. Superionicity may be aided by the large size, quasispherical shape, and high rotational mobility of the B12H12(2-) anions.

Characterization of medicinal compounds confined in porous media by neutron vibrational spectroscopy and first-principles calculations: a case study with ibuprofen.

Purpose: Amorphous formulations of ibuprofen were prepared by confining the drug molecules into the porous scaffolds. The molecular interactions between ibuprofen and porous media were investigated using neutron vibrational spectroscopy.

Methods: Ibuprofen was introduced into the pores using sublimation and adsorption method.

Raman, FTIR, photoacoustic-infrared, and inelastic neutron scattering spectra of ternary metal hydride salts A2MH5, (A = Ca, Sr, Eu; M = Ir, Rh) and their deuterides.

The vibrational spectra of the ternary metal hydride (deuteride) salts, A(2)MH(5) and A(2)MD(5), where A = calcium, strontium and europium and M = iridium(I) and rhodium(I), have been assigned using Raman, Fourier transform infrared, photoacoustic infrared, and inelastic neutron scattering spectroscopies and density functional theory (DFT) calculations. The wavenumbers of the infrared-active stretching vibrations depend upon the ionization energies of the central metal atom and the cation. The phase transition in calcium pentahydridoiridate(I) was studied as a function of temperature and pressure.

Monoammoniate of calcium amidoborane: synthesis, structure, and hydrogen-storage properties.

The monoammoniate of calcium amidoborane, Ca(NH(2)BH(3))(2)·NH(3), was synthesized by ball milling an equimolar mixture of CaNH and AB. Its crystal structure has been determined and was found to contain a dihydrogen-bonded network. Thermal decomposition under an open-system begins with the evolution of about 1 equivalent/formula unit (equiv.

Hydrogen dynamics in Ce2Fe17H5: inelastic and quasielastic neutron scattering studies.

The vibrational spectrum of hydrogen and the parameters of H jump motion in the rhombohedral Th(2)Zn(17)-type compound Ce(2)Fe(17)H(5) have been studied by means of inelastic and quasielastic neutron scattering. It is found that hydrogen atoms occupying interstitial Ce(2)Fe(2) sites participate in the fast localized jump motion over the hexagons formed by these tetrahedral sites. The H jump rate τ(-1) of this localized motion is found to change from 3.

Low-temperature tunneling and rotational dynamics of the ammonium cations in (NH4)2B12H12.

Low-temperature neutron scattering spectra of diammonium dodecahydro-closo-dodecaborate [(NH(4))(2)B(12)H(12)] reveal two NH(4)(+) rotational tunneling peaks (e.g., 18.