Analysis of Dihydrogen Bonding in Ammonium Borohydride
Journal article, 2019

The structural and vibrational properties of ammonium borohydride, NH4BH4, have been examined by first-principles density functional theory (DFT) calculations and inelastic neutron scattering (INS). The H disordered crystal structure of NH4BH4 is composed of the tetrahedral complex ions NH4+ and BH4-, which are arranged as in the fcc NaCl structure and linked by intermolecular dihydrogen bonding. Upon cooling, the INS spectra revealed a structural transition between 45 and 40 K. The reversible transition occurs upon heating between 46 and 49 K. In the low-temperature form reorientational dynamics are frozen. The libration modes for BH4- and NH4+ are near 300 and 200 cm(-1), respectively. Upon entering the fcc high-temperature form, NH4+ ions attain fast reorientational dynamics, as indicated in the disappearance of the NH4+ libration band, whereas BH4- ions become significantly mobile only at temperatures above 100 K. The vibrational behavior of BH4- ions in NH4BH4 compares well to the heavier alkali metal borohydrides, NaBH4-CsBH4. DFT calculations revealed a nondirectional nature of the dihydrogen bonding in NH4BH4 with only weak tendency for long-range order. Different rotational configurations of complex ions appear quasi-degenerate, which is reminiscent of glasses.


Stanislav Filippov

Stockholm University

Linköping University

Jakob B. Grinderslev

Aarhus University

Mikael Andersson

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Jeff Armstrong

STFC Rutherford Appleton Laboratory

Maths Karlsson

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Torben R. Jensen

Aarhus University

Johan Klarbring

Linköping University

Sergei I. Simak

Linköping University

Ulrich Haussermann

Stockholm University

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 123 47 28631-28639

Subject Categories

Inorganic Chemistry

Theoretical Chemistry

Condensed Matter Physics



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3/2/2022 1