Static Compression of Tetramethylammonium Borohydride

Journal Article · Tue Nov 15 04:00:00 EST 2011 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp204642b· OSTI ID:1029400

Dalton, Douglas Allen; Somayazulu, M; Goncharov, Alexander F; Hemley, Russell J ^[1]

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1. CIW

Raman spectroscopy and synchrotron X-ray diffraction are used to examine the high-pressure behavior of tetramethylammonium borohydride (TMAB) to 40 GPa at room temperature. The measurements reveal weak pressure-induced structural transitions around 5 and 20 GPa. Rietveld analysis and Le Bail fits of the powder diffraction data based on known structures of tetramethylammonium salts indicate that the transitions are mediated by orientational ordering of the BH{sub 4}{sup -} tetrahedra followed by tilting of the (CH{sub 3}){sub 4}N{sup +} groups. X-ray diffraction patterns obtained during pressure release suggest reversibility with a degree of hysteresis. Changes in the Raman spectrum confirm that these transitions are not accompanied by bonding changes between the two ionic species. At ambient conditions, TMAB does not possess dihydrogen bonding, and Raman data confirms that this feature is not activated upon compression. The pressure-volume equation of state obtained from the diffraction data gives a bulk modulus [K{sub 0} = 5.9(6) GPa, K'{sub 0} = 9.6(4)] slightly lower than that observed for ammonia borane. Raman spectra obtained over the entire pressure range (spanning over 40% densification) indicate that the intramolecular vibrational modes are largely coupled.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSFOTHERDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1029400
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 40 Vol. 115; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AMMONIA
BONDING
BOROHYDRIDES
COMPRESSION
DIFFRACTION
HYSTERESIS
PRESSURE RANGE
PRESSURE RELEASE
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SYNCHROTRONS
X-RAY DIFFRACTION