High-density strontium hydride: An experimental and theoretical study |
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| Authors: | Jesse S. Smith Serge Desgreniers Dennis D. Klug John S. Tse |
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| Affiliation: | 1. Laboratoire de physique des solides denses, Department of Physics, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5;2. Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6;3. Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2;1. Applied Physics Laboratory, University of Ibn Khaldoun, Tiaret, Algeria;2. LSF, University of Laghouat, Laghouat 03, Algeria;3. USEK – CSR – CNRSL, Kaslik-Jounieh, Lebanon;4. CNRS, ICMCB, UPR 9048, F-33600 Pessac, France;5. Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac, France;1. School of Materials Science and Engineering, Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou, 510641, PR China;2. China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou, 510641, PR China;3. Australian Synchrotron, 800 Blackburn Rd., Clayton 3168, Australia;2. General Motors Research and Development, 30500 Mound Road, Warren, MI 48090, USA |
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| Abstract: | Powder x-ray diffraction experiments and first-principles calculations have been carried out to investigate the possibility of a structural phase transition, characterized by a change from ionic to covalent bonding, in strontium hydride at pressures greater than 50 GPa. The powder x-ray diffraction results confirm a previously reported transition from the cotunnite structure to the Ni2In structure at approximately 8 GPa. The Ni2In phase remained stable up to the maximum experimental pressure of 113 GPa. The first-principles calculations, however, predict that under hydrostatic conditions a transition from the Ni2In structure to the AlB2 structure will occur at 115 GPa. A comparison of the pressure-dependent volume yielded by the respective experimental and theoretical studies suggests that in many cases the bulk modulus obtained from experiments carried out under non-hydrostatic conditions may be overestimated. Raman spectroscopy experiments corroborated the previously proposed Ni2In structure, as the spectra obtained at pressures greater than 8 GPa exhibited two Raman-active modes, consistent with those expected from the Ni2In structure. |
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