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Neutron vibrational spectroscopy and first-principles calculations of the ternary hydrides Li4Si2H(D) and Li4Ge2H(D): Electronic structure and lattice dynamics

Wu, Hui and Zhou, Wei and Udovic, Terrence J. and Rush, John J. and Yildirim, Taner and Hartman, Michael R. and Bowman, Robert C., Jr. and Vajo, John J. (2007) Neutron vibrational spectroscopy and first-principles calculations of the ternary hydrides Li4Si2H(D) and Li4Ge2H(D): Electronic structure and lattice dynamics. Physical Review B, 76 (22). Art. No. 224301. ISSN 1098-0121. https://resolver.caltech.edu/CaltechAUTHORS:WUHprb07

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Abstract

Using combined neutron spectroscopy and first-principles calculations, we investigated the electronic structure and vibrational dynamics of the recently discovered class of ternary hydrides Li4Tt2H (Tt=Si and Ge). In these compounds, all hydrogen atoms are located in a single type of Li6-defined octahedral site. The Tt atoms form long-range Tt-Tt chains sandwiched between each Li6-octahedra layer. The Li-H interactions are strongly ionic, with bond lengths comparable to those in LiH. Our density functional theory calculations indicate that Li atoms transfer their electrons to both H and Tt atoms. Tt atoms within the Tt-Tt chain are bonded covalently. The electronic density of states reveals that both hydrides exhibit metallic behavior. The observed vibrational spectra of these hydrides are in good overall agreement with the calculated phonon modes. There is evidence of dispersion induced splitting in the optical phonon peaks that can be ascribed to the coupling of H vibrations within the Li6-octahedra layers.


Item Type:Article
ORCID:
AuthorORCID
Bowman, Robert C., Jr.0000-0002-2114-1713
Additional Information:© 2007 The American Physical Society. (Received 21 May 2007; accepted 7 August 2007; published 17 December 2007) This work was partially supported by DOE through EERE Grant No. DE-AI-01-05EE11104 (H.W. and T.J.U.), EERE Grant No. DE-FC36-04GO14282 (W.Z.), BES Grant No. DE-FG02-98ER45701 (W.Z., T.Y.), and EERE Grant No. DE-AI-01-06EE11105 (R.C.B) and was partially performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautical and Space Administration.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-AI-01-05EE11104
Department of Energy (DOE)DE-FC36-04GO14282
Department of Energy (DOE)DE-FG02-98ER45701
Department of Energy (DOE)DE-AI-01-06EE11105
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:bond lengths; density functional theory; electronic density of states; lattice dynamics; lithium compounds; phonon dispersion relations; vibrational modes
Issue or Number:22
Record Number:CaltechAUTHORS:WUHprb07
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:WUHprb07
Alternative URL:http://dx.doi.org/10.1103/PhysRevB.76.224301
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9418
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:20 Dec 2007
Last Modified:03 Oct 2019 00:00

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