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Title: First-principles calculated decomposition pathways for LiBH 4 nanoclusters

Here, we analyze thermodynamic stability and decomposition pathways of LiBH 4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH 4) n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li) n, (B) n, (LiB) n, (LiH) n, and Li 2B nH n; 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 LiBH 4. While experiments have found that the bulk material decomposes into LiH and B, with Li 2B 12H 12 as a kinetically inhibited intermediate phase, (LiBH 4) n nanoclusters with n ≤ 12 are predicted to decompose into mixed Li nB n clusters via a series of intermediate clusters of Li nB nH m (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 destabilizationmore » of reaction products.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3]
  1. National Sun Yat-Sen Univ., Kaohsiung (Taiwan). Dept. of Physics
  2. Univ. of Missouri-St. Louis, St. Louis, MO (United States). Center for Nanoscience and Dept. of Physics and Astronomy
  3. Univ. of California Los Angeles, Los Angeles, CA (United States). Dept. of Materials Science and Engineering
Publication Date:
Grant/Contract Number:
FG02-07ER46433; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
National Sun Yat-Sen Univ., Kaohsiung (Taiwan)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; reversible hydrogen storage; nanoporous carbon; lithium clusters; b-n; destabilization; release; dehydrogenation; nanoparticles; desorption; stability
OSTI Identifier:
1283014