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Title: High-pressure structural parameters and equation of state of osmium to 207 GPa

We studied the most incompressible transition metal osmium (Os) under high pressure. There is significant interest in Os because of the structural anomalies attributed to topological transitions in the Fermi surface for valence electrons in the hexagonal close-packed phase. We report on measurements of structural parameters and equation of state on Os metal to a pressure of 207 GPa at ambient temperature using platinum as a pressure standard. We also obtained angle-dispersive X-ray diffraction data at a synchrotron source with closely spaced pressure intervals to observe any discontinuities or anomalies in the axial c/a ratio at high pressures. Rietveld refinements of X-ray diffraction data show a slowly varying axial ratio (c/a) with a broad minimum at 75 GPa. Our data do not provide any evidence of anomalous behavior in the c/a ratio in Os at 25 or 150 GPa as have been reported in previous studies. These experimental results are in agreement with theoretical calculations that do not predict any anomalous behavior in c/a ratio in Os under extreme conditions. We present an equation of state for Os to 207 GPa (V/V 0 = 0.761) at ambient temperature and compare our results with the previously published data.
Authors:
 [1] ; ORCiD logo [2] ;  [1] ;  [3]
  1. Univ. of Alabama, Birmingham, AL (United States). Dept. of Physics
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Shock and Detonation Physics Group (M-9)
  3. Uppsala Univ. (Sweden)
Publication Date:
Report Number(s):
LA-UR-17-27962
Journal ID: ISSN 2331-1940
Grant/Contract Number:
AC52-06NA25396; NA0001974; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Cogent Physics
Additional Journal Information:
Journal Volume: 4; Journal Issue: 1; Journal ID: ISSN 2331-1940
Publisher:
Cogent OA
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; high pressure, osmium, diamond anvil cell
OSTI Identifier:
1398935