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Dimitrievska, M.; Shea, P.; Kweon, K.E.; Bercx, M.; Varley, J.B.; Tang, W.S.; Skripov, A.V.; Stavila, V.; Udovic, T.J.; Wood, B.C. |
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Title |
Carbon Incorporation and Anion Dynamics as Synergistic Drivers for Ultrafast Diffusion in Superionic LiCB11H12 and NaCB11H12 |
Type |
A1 Journal article |
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Year  |
2018 |
Publication |
Advanced energy materials |
Abbreviated Journal |
Adv Energy Mater |
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Volume |
8 |
Issue |
15 |
Pages |
1703422 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
The disordered phases of LiCB11H12 and NaCB11H12 possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB11H12- anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. The symmetry-breaking carbon atom in CB11H12- also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 x 10(10) s(-1), suggesting the underlying energy landscape fluctuates dynamically on diffusion-relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon-modified cation-anion interaction accounts for the higher ionic conductivity in CB11H12- salts compared with B12H122-. |
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Publisher |
WILEY-VCH Verlag GmbH & Co. |
Place of Publication |
Weinheim |
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Wos |
000434031400026 |
Publication Date |
2018-02-21 |
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ISSN |
1614-6832; 1614-6840 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
16.721 |
Times cited |
20 |
Open Access |
OpenAccess |
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Notes |
; This work was performed in part under the auspices of the U.S. Department of Energy at Lawrence Livermore National Laboratory (LLNL) under Contract No. DE-AC52-07NA27344 and funded by Laboratory Directed Research and Development Grant 15-ERD-022. Computing support came from the LLNL Institutional Computing Grand Challenge program. This work was also performed in part within the assignment of the Russian Federal Agency of Scientific Organizations (program “Spin” No. 01201463330). The authors gratefully acknowledge support from the Russian Foundation for Basic Research under Grant No. 15-03-01114 and the Ural Branch of the Russian Academy of Sciences under Grant No. 15-9-2-9. A.V.S. gratefully acknowledges travel support from CRDF Global in conjunction with this work under Grant No. FSCX-15-61826-0. M.D. gratefully acknowledges research support from the Hydrogen Materials-Advanced Research Consortium (HyMARC), established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, under Contract No. DE-AC36-08GO28308. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-1508249. The views, opinions, findings, and conclusions stated herein are those of the authors and do not necessarily reflect those of CRDF Global, or the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. ; |
Approved |
Most recent IF: 16.721 |
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Call Number |
UA @ lucian @ c:irua:152045 |
Serial |
5015 |
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Author |
Ban, V.; Soloninin, A.V.; Skripov, A.V.; Hadermann, J.; Abakumov, A.; Filinchuk, Y. |
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Title |
Pressure-Collapsed Amorphous Mg(BH4)(2): An Ultradense Complex Hydride Showing a Reversible Transition to the Porous Framework |
Type |
A1 Journal article |
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Year |
2014 |
Publication |
The journal of physical chemistry: C : nanomaterials and interfaces |
Abbreviated Journal |
J Phys Chem C |
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Volume |
118 |
Issue |
40 |
Pages |
23402-23408 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
Hydrogen-storage properties of complex hydrides depend of their form, such as a polymorphic form or an eutectic mixture. This Paper reports on an easy and reproducible way to synthesize a new stable form of magnesium borohydride by pressure-induced collapse of the porous gamma-Mg(BH4)(2). This amorphous complex hydride was investigated by temperature-programmed synchrotron X-ray diffraction (SXRD), transmission electron microscopy (TEM), thermogravimetric analysis, differential scanning calorimetry analysis, and Raman spectroscopy, and the dynamics of the BH4 reorientation was studied by spinlattice relaxation NMR spectroscopy. No long-range order is observed in the lattice region by Raman spectroscopy, while the internal vibration modes of the BH4 groups are the same as in the crystalline state. A hump at 4.9 angstrom in the SXRD pattern suggests the presence of nearly linear MgBH4 Mg fragments constituting all the known crystalline polymorphs of Mg(BH4)(2), which are essentially frameworks built of tetrahedral Mg nodes and linear BH4 linkers. TEM shows that the pressure-collapsed phase is amorphous down to the nanoscale, but surprisingly, SXRD reveals a transition at similar to 90 degrees C from the dense amorphous state (density of 0.98 g/cm(3)) back to the porous ? phase having only 0.55 g/cm(3) crystal density. The crystallization is slightly exothermic, with the enthalpy of -4.3 kJ/mol. The volumetric hydrogen density of the amorphous form is 145 g/L, one of the highest among hydrides. Remarkably, this form of Mg(BH4)2 has different reactivity compared to the crystalline forms. The parameters of the reorientational motion of BH4 groups in the amorphous Mg(BH4)(2) found from NMR measurements differ significantly from those in the known crystalline forms. The behavior of the nuclear spinlattice relaxation rates can be described in terms of a Gaussian distribution of the activation energies centered on 234 +/- 9 meV with the dispersion of 100 +/- 10 meV. |
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Place of Publication |
Washington, D.C. |
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Wos |
000343016800067 |
Publication Date |
2014-09-26 |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1932-7447;1932-7455; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.536 |
Times cited |
23 |
Open Access |
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Notes |
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Approved |
Most recent IF: 4.536; 2014 IF: 4.772 |
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Call Number |
UA @ lucian @ c:irua:121113 |
Serial |
2711 |
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