First-principles insight into the degeneracy of ground-state LiBH<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>structures

Zhang, Yongsheng; Wang, Yongli; Michel, Kyle; Wolverton, Chris

doi:10.1103/physrevb.86.094111

Cited by 10 publications

(4 citation statements)

References 24 publications

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“…Upon DFT relaxation of the experimental crystal structure of LiBH 4 , the lattice parameters, a, b, and c are 7.32, 4.38 and 6.58Å, respectively, which are within 2.8% of experimental values (table I). Moreover, the DFT-relaxed LiBH 4 atomic positions are in fairly good agreement with the experimental data, and our calculations also support the recent theoretical study of Zhang et al 50 . Zhang et al show that the experimentally observed Pnma LiBH 4 structure is the lowest in energy in DFT.…”

Section: B Determining Hydrogen Desorption Reactionssupporting

confidence: 80%

First-principles studies of phase stability and crystal structures in Li-Zn mixed-metal borohydrides

2013

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We address the problem of finding mixed metal borohydrides with favorable thermodynamics and illustrate the approach using the example of LiZn 2 (BH 4 ) 5 . Using density functional theory (DFT), along with the grand canonical linear programming method (GCLP), we examine the experimentally and computationally proposed crystal structures and the finite-temperature thermodynamics of dehydrogenation for the quaternary hydride LiZn 2 (BH 4 ) 5 . We find the following: (i) For LiZn 2 (BH 4 ) 5 , DFT calculations of the experimental crystal structures reveal that the structure from the neutron diffraction experiments of Ravnsbaek et al. is more stable [by 24 kJ/(mol f.u.)] than that based on a previous X-ray study. (ii) Our DFT calculations show that when using the neutron-diffraction structure of

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Section: B Determining Hydrogen Desorption Reactionssupporting

confidence: 80%

First-principles studies of phase stability and crystal structures in Li-Zn mixed-metal borohydrides

2013

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“…Bulk lithium is calculated in the body-centered cubic lattice, bulk boron is in the α -B phase, and bulk LiH is in the rocksalt structure. Bulk LiBH 4 has several near-degenerate ground-state structures 36 , and the Pnma structure is used in our calculations 37 . As for bulk LiB, we used a P 6 3 / mmc structure reported in a previous experimental study 38 .…”

Section: Resultsmentioning

confidence: 99%

First-principles calculated decomposition pathways for LiBH4 nanoclusters

Huang

Chen

Chuang

et al. 2016

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We analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathways markedly differ from those in bulk LiBH4. While experiments have found that the bulk material decomposes into LiH and B, with Li2B12H12 as a kinetically inhibited intermediate phase, (LiBH4)n nanoclusters with n ≤ 12 are predicted to decompose into mixed LinBn clusters via a series of intermediate clusters of LinBnHm (m ≤ 4n). The calculated pressure-composition isotherms and temperature-pressure isobars exhibit sloping plateaus due to finite size effects on reaction thermodynamics. Generally, decomposition temperatures of free-standing clusters are found to increase with decreasing cluster size due to thermodynamic destabilization of reaction products.

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“…Density-functional theory (DFT) has been used to accurately study a wide range of thermodynamic and kinetic properties of many H 2 storage materials. ,,− For a series of metal complex hydrides, the hydrogen release enthalpies from DFT with the generalized gradient approximation (GGA) are typically within ∼10 kJ/(mol H 2 ) of experimental values. , We perform DFT calculations using the Vienna Ab Initio Simulation Package (VASP) code with the projector augmented wave (PAW) scheme and the generalized gradient approximation of Perdew, Burke, and Ernzerhof (GGA-PBE) for the exchange-correlation functional. The energy cutoff we use for the plane wave expansion is 800 eV.…”

Section: Methodsmentioning

confidence: 99%

First-Principles Prediction of Intermediate Products in the Decomposition of Metal Amidoboranes

2012

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The nonvolatile products remaining after the thermal decomposition of metal amidoboranes (MAB, M = metal) are amorphous and incompletely characterized, increasing the complexity of devising regeneration strategies for these potential hydrogen storage materials. Utilizing the combined prototype electrostatic ground state search and density-functional theory (PEGS+DFT), we find that potential reaction products ([NHBH2]−, [NBH]−, [N3H2B3H3]−, and polymer-M[NHBH2] anion groups) in the decomposition of LiAB and CaAB are calculated to be significantly endothermic, in contrast to the experimentally measured nearly thermoneutral values [∼−4 kJ/(mol H2) in LiAB and 3.5 kJ/(mol H2) in CaAB], suggesting that there are alternative products formed. The dianion group [NHBHNHBH3]2– has recently been suggested to form in the decomposition of a calcium amidoborane complex in solution. In LiAB and CaAB, we use PEGS+DFT to predict intermediate metal–dianion compounds, and the static H2 release enthalpy is 27.4 and 27.3 kJ/(mol H2) in LiAB and CaAB, respectively. Introducing vibrational effects by phonon calculations, the enthalpies are shifted down by a roughly constant amount, ∼25 and ∼22 kJ/(mol H2) at 0 and 300 K. Thus, our theoretical H2 release enthalpies agree with the experimentally measured nearly thermoneutral data in the decomposition of LiAB and CaAB. This agreement supports the existence of the dianion phases as products in the decomposition of metal amidoboranes. Then, using the dianion compound as an intermediate in the decomposition of MAB, we further study the stability trends of a series of MAB (M = Li, Na, K, Ca).

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First-principles insight into the degeneracy of ground-state LiBH4structures

Cited by 10 publications

References 24 publications

First-principles studies of phase stability and crystal structures in Li-Zn mixed-metal borohydrides

First-principles studies of phase stability and crystal structures in Li-Zn mixed-metal borohydrides

First-principles calculated decomposition pathways for LiBH4 nanoclusters

First-Principles Prediction of Intermediate Products in the Decomposition of Metal Amidoboranes

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