Structural phase transition in CaH[sub 2] at high pressures

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DOIResolve DOI: http://doi.org/10.1103/PhysRevB.75.134108
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TypeArticle
Journal titlePhys. Rev. B
Physical Review B (Condensed Matter and Materials Physics)
Volume75
Issue13
Pages1341085; # of pages: 134104
Subjectab initio calculations; calcium compounds; crystal structure; high-pressure solid-state phase transformations; hydrogen storage
AbstractThe structural and vibrational properties of CaH2 have been examined up to 30 GPa at room temperature. Under ambient conditions, CaH2 has a Pnma (cotunnite-type) structure. A structural phase transformation was observed around 15 GPa and completed at 20 GPa. The high pressure structure is identified as hexagonal P63/mmc. First-principles calculations reproduced the first-order nature of the transition. Since P63/mmc is a supergroup of Pnma the structural change can be traced back to gradual displacements of the hydrogen atoms from the 4c positions in the cotunnite structure to the special 2a and 2d positions in the hexagonal structure. The observed phase transition pressure is much lower than that predicted for MgH2.
Publication date
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences; NRC Genomics and Health Initiative
Peer reviewedNo
NPARC number12328372
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Record identifier301dbf7d-d26f-4ab6-ad31-c8b37ee7d372
Record created2009-09-10
Record modified2016-05-09
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