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Title: New Calcium Hydrides with Mixed Atomic and Molecular Hydrogen

Abstract

In this study, two new polyhydrides of calcium have been synthesized at high pressures and high temperatures and characterized by Raman spectroscopy, infrared spectroscopy, and synchrotron X-ray diffraction. Above 20 GPa and 700 K, we synthesize a phase having a monoclinic (C2/m) structure with Ca 2H 5 composition, which is characterized by a distinctive vibration at 3789 cm –1 at 25 GPa. The observed Raman spectrum is in close agreement with first-principles calculations of a Ca 2H 5 structure characterized by a lattice containing a central layer of H 2 molecules oriented along the (100) direction. At higher pressures (e.g., 116 GPa and 1600 K), we synthesize another phase, which has the composition of CaH 4 and a denser body-centered tetragonal structure. This weakly metallic phase also contains molecular-like H 2 units, and its spectroscopic as well as diffraction signatures match closely with those predicted from first-principles calculations. This phase is observed to persist on decompression to 60 GPa at room temperature. Lastly, the elongation of the H–H bond in these hydrides is a result of the Ca–H 2 interaction, analogous to what occurs in molecular compounds, where H 2 binds side-on to a d-element, such as in Kubas complex.

Authors:
 [1];  [1]; ORCiD logo [1];  [1]; ORCiD logo [2];  [3];  [1];  [4]; ORCiD logo [5]; ORCiD logo [3]
  1. Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Laboratory
  2. Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Laboratory; George Washington Univ., Washington, DC (United States). Institute of Materials Science and Department of Civil and Environmental Engineering
  3. George Washington Univ., Washington, DC (United States). Institute of Materials Science and Department of Civil and Environmental Engineering
  4. Argonne National Lab. (ANL), Argonne, IL (United States). HPCAT, X-ray Sciences Division
  5. University at Buffalo, State University of New York, Buffalo, NY (United States). Department of Chemistry
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Energy Frontier Research in Extreme Environments (EFree); Argonne National Lab. (ANL), Argonne, IL (United States); Carnegie Inst. of Washington, Washington, DC (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1481418
Alternate Identifier(s):
OSTI ID: 1637923
Grant/Contract Number:  
AC02-06CH11357; SC0001057; NA0002006; NA0001974; FG02-99ER45775
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 34; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 08 HYDROGEN

Citation Formats

Mishra, Ajay K., Muramatsu, Takaki, Liu, Hanyu, Geballe, Zachary M., Somayazulu, Maddury, Ahart, Muhtar, Baldini, Maria, Meng, Yue, Zurek, Eva, and Hemley, Russell J. New Calcium Hydrides with Mixed Atomic and Molecular Hydrogen. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b05030.
Mishra, Ajay K., Muramatsu, Takaki, Liu, Hanyu, Geballe, Zachary M., Somayazulu, Maddury, Ahart, Muhtar, Baldini, Maria, Meng, Yue, Zurek, Eva, & Hemley, Russell J. New Calcium Hydrides with Mixed Atomic and Molecular Hydrogen. United States. https://doi.org/10.1021/acs.jpcc.8b05030
Mishra, Ajay K., Muramatsu, Takaki, Liu, Hanyu, Geballe, Zachary M., Somayazulu, Maddury, Ahart, Muhtar, Baldini, Maria, Meng, Yue, Zurek, Eva, and Hemley, Russell J. Tue . "New Calcium Hydrides with Mixed Atomic and Molecular Hydrogen". United States. https://doi.org/10.1021/acs.jpcc.8b05030. https://www.osti.gov/servlets/purl/1481418.
@article{osti_1481418,
title = {New Calcium Hydrides with Mixed Atomic and Molecular Hydrogen},
author = {Mishra, Ajay K. and Muramatsu, Takaki and Liu, Hanyu and Geballe, Zachary M. and Somayazulu, Maddury and Ahart, Muhtar and Baldini, Maria and Meng, Yue and Zurek, Eva and Hemley, Russell J.},
abstractNote = {In this study, two new polyhydrides of calcium have been synthesized at high pressures and high temperatures and characterized by Raman spectroscopy, infrared spectroscopy, and synchrotron X-ray diffraction. Above 20 GPa and 700 K, we synthesize a phase having a monoclinic (C2/m) structure with Ca2H5 composition, which is characterized by a distinctive vibration at 3789 cm–1 at 25 GPa. The observed Raman spectrum is in close agreement with first-principles calculations of a Ca2H5 structure characterized by a lattice containing a central layer of H2 molecules oriented along the (100) direction. At higher pressures (e.g., 116 GPa and 1600 K), we synthesize another phase, which has the composition of CaH4 and a denser body-centered tetragonal structure. This weakly metallic phase also contains molecular-like H2 units, and its spectroscopic as well as diffraction signatures match closely with those predicted from first-principles calculations. This phase is observed to persist on decompression to 60 GPa at room temperature. Lastly, the elongation of the H–H bond in these hydrides is a result of the Ca–H2 interaction, analogous to what occurs in molecular compounds, where H2 binds side-on to a d-element, such as in Kubas complex.},
doi = {10.1021/acs.jpcc.8b05030},
url = {https://www.osti.gov/biblio/1481418}, journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 34,
volume = 122,
place = {United States},
year = {2018},
month = {7}
}

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