First-principles insight into the degeneracy of ground-state LiBH4 structures

Yongsheng Zhang, Yongli Wang, Kyle Michel, and C. Wolverton
Phys. Rev. B 86, 094111 – Published 19 September 2012

Abstract

Recently, a number of ground-state structures of LiBH4 have been proposed, both from experimental and computational works. The results show controversy between computational and experimental ground-state crystal structures of LiBH4. In order to determine which is truly the lowest in energy, we study LiBH4 in a variety of crystal structures using density functional theory (DFT) calculations of the free energy (T=0 K total energy plus vibrational thermodynamics), employing a variety of DFT methods and exchange-correlation functionals. Our calculations show that the experimentally observed structures are lowest in energy in DFT. However, multiple LiBH4 structures are degenerate with the experimental ground-state crystal structure and there exists a relatively flat potential energy landscape between them. These degenerate structures include the recently theoretically predicted LiBH4 structure [Tekin, Caputo, and Züettel, Phys. Rev. Lett. 104, 215501 (2010)], which the authors claimed to be 9.66 kJ/(mol LiBH4) (or 100 meV/fu) lower in energy than the experimentally XRD determined LiBH4 structure [Soulié, Renaudin, Černý, and Yvon, J. Alloys Compd. 346, 200 (2002)]. Our calculations do not support these previous claims, and hence resolve this discrepancy between DFT and experiment.

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  • Received 6 June 2012

DOI:https://doi.org/10.1103/PhysRevB.86.094111

©2012 American Physical Society

Authors & Affiliations

Yongsheng Zhang, Yongli Wang, Kyle Michel, and C. Wolverton

  • Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA

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Issue

Vol. 86, Iss. 9 — 1 September 2012

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