High-pressure phase and transition phenomena in ammonia borane NH3 BH3 from x-ray diffraction, Landau theory, and ab initio calculations
(2009) Physical Review B - Condensed Matter and Materials Physics — Vol. 79, n° 21, p. 1-11 (2009)
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- Abstract
- Structural evolution of a prospective hydrogen storage material, ammonia borane NH3 BH3, has been studied at high pressures up to 12 GPa and at low temperatures by synchrotron powder diffraction. At 293 K and above 1.1 GPa a disordered I4mm structure reversibly transforms into a new ordered phase. Its Cmc 21 structure was solved from the diffraction data; the positions of N and B atoms and the orientation of NH3 and BH3 groups were finally assigned with the help of density-functional theory calculations. Group-theoretical analysis identifies a single two-component order parameter, combining ordering and atomic displacement mechanisms, which link an orientationally disordered parent phase I4mm with ordered distorted Cmc 21, Pmn 21, and P 21 structures. We propose a generic phase diagram for NH3 BH3, mapping three experimentally found and one predicted (P 21) phases as a function of temperature and pressure, along with the evolution of the corresponding structural distortions. Ammonia borane belongs to the class of improper ferroelastics and we show that both temperature- and pressure-induced phase transitions can be driven to be of the second order. The role of N-H...H-B dihydrogen bonds and other intermolecular interactions in the stability of NH3 BH3 polymorphs is examined. © 2009 The American Physical Society.
- Affiliations
ESRF, Grenoble (France) Chimie
Citations
Filinchuk, Y., Nevidomskyy, A. H., Chernyshov, D., & Dmitriev, V. (2009). High-pressure phase and transition phenomena in ammonia borane NH3 BH3 from x-ray diffraction, Landau theory, and ab initio calculations. Physical Review B - Condensed Matter and Materials Physics, 79(21), 1-11. https://doi.org/10.1103/PhysRevB.79.214111 (Original work published 2009)