Journal
PHYSICAL REVIEW B
Volume 86, Issue 9, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.86.094111
Keywords
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Funding
- US Department of Energy [DE-FC36-08GO18136, DE-FG02-07ER46433]
- Ford Motor Company
- U.S. Department of Energy (DOE) [DE-FG02-07ER46433] Funding Source: U.S. Department of Energy (DOE)
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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 Zuettel, Phys. Rev. Lett. 104, 215501 (2010)], which the authors claimed to be 9.66 kJ/(mol LiBH4) (or similar to 100 meV/fu) lower in energy than the experimentally XRD determined LiBH4 structure [Soulie, Renaudin, Cerny, 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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