TY - JOUR
T1 - First-principles insight into the degeneracy of ground-state LiBH 4 structures
AU - Zhang, Yongsheng
AU - Wang, Yongli
AU - Michel, Kyle
AU - Wolverton, C.
PY - 2012/9/19
Y1 - 2012/9/19
N2 - Recently, a number of ground-state structures of LiBH 4 have been proposed, both from experimental and computational works. The results show controversy between computational and experimental ground-state crystal structures of LiBH 4. In order to determine which is truly the lowest in energy, we study LiBH 4 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 LiBH 4 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 4 structure, which the authors claimed to be 9.66 kJ/(mol LiBH 4) (or ∼100 meV/fu) lower in energy than the experimentally XRD determined LiBH 4 structure. Our calculations do not support these previous claims, and hence resolve this discrepancy between DFT and experiment.
AB - Recently, a number of ground-state structures of LiBH 4 have been proposed, both from experimental and computational works. The results show controversy between computational and experimental ground-state crystal structures of LiBH 4. In order to determine which is truly the lowest in energy, we study LiBH 4 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 LiBH 4 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 4 structure, which the authors claimed to be 9.66 kJ/(mol LiBH 4) (or ∼100 meV/fu) lower in energy than the experimentally XRD determined LiBH 4 structure. Our calculations do not support these previous claims, and hence resolve this discrepancy between DFT and experiment.
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U2 - 10.1103/PhysRevB.86.094111
DO - 10.1103/PhysRevB.86.094111
M3 - Article
AN - SCOPUS:84866661280
SN - 1098-0121
VL - 86
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 9
M1 - 094111
ER -