Abstract
Recently, a number of ground-state structures of LiBH have been proposed, both from experimental and computational works. The results show controversy between computational and experimental ground-state crystal structures of LiBH. In order to determine which is truly the lowest in energy, we study LiBH in a variety of crystal structures using density functional theory (DFT) calculations of the free energy ( 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 LiBH 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 LiBH structure [Tekin, Caputo, and Züettel, Phys. Rev. Lett. 104, 215501 (2010)], which the authors claimed to be 9.66 kJ/(mol LiBH) (or 100 meV/fu) lower in energy than the experimentally XRD determined LiBH 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.
- Received 6 June 2012
DOI:https://doi.org/10.1103/PhysRevB.86.094111
©2012 American Physical Society