Abstract

We have studied the crystal structure of fully deuterated BH3NH3 using powder neutron diffraction at different temperatures. It is evident that an order-disorder phase transition occurs around 225 K. At low temperature, the compound crystallizes in the orthorhombic structure with space group Pnm21 and gradually transforms to a high temperature tetragonal structure with space group I4 mm above 225 K. At 16 K, the BD3-ND3 unit stacks along the c axis with a tilt angle of about 16° between the N-B bond and the c axis. As the temperature is increased, the BD3-ND3 groups start to reorient along the c axis and the deuterium atoms become disordered, leading to the tetragonal phase transition.

Department(s)

Physics

Second Department

Chemistry

Sponsor(s)

United States. Department of Energy

Keywords and Phrases

Ammonia; Crystal Structure; Crystallisation; Hydrogen Storage; Order-Disorder Transformations; Space Groups; Crystallization

International Standard Serial Number (ISSN)

0003-6951

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2008 American Institute of Physics (AIP), All rights reserved.

Included in

Chemistry Commons

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