Pressure-induced phase and chemical transformations of lithium peroxide (Li₂O₂ )

Journal Article · Wed Aug 24 00:00:00 EDT 2016 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4961453· OSTI ID:1467875

Dunuwille, Mihindra ^[1]; Kim, Minseob ^[1]; Yoo, Choong-Shik ^[1]

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1. Washington State Univ., Pullman, WA (United States). Dept. of Chemistry and Inst. for Shock Physics

Here, we present the pressure-induced phase/chemical changes of lithium peroxide (Li₂O₂) to 63 GPa using diamond anvil cells, confocal micro-Raman spectroscopy, and synchrotron x-ray diffraction. The Raman data show the emergence of the major vibrational peaks associated with O₂ above 30 GPa, indicating the subsequent pressure-induced reversible chemical decomposition (disassociation) in dense Li₂O₂. The x-ray diffraction data of Li₂O₂, on the other hand, show no dramatic structural change but remain well within a P6₃/mmc structure to 63 GPa. Nevertheless, the Rietveld refinement indicates a subtle change in the structural order parameter z of the oxygen position O (1/3, 2/3, z) at around 35 GPa, which can be considered as a second-order, isostructural phase transition. The nearest oxygen-oxygen distance collapses from 1.56 Å at ambient condition to 1.48 Å at 63 GPa, resulting in a more ionic character of this layered crystal lattice, 3Li⁺+(LiO₂)$$3-\atop{3}$$. This structural change in turn advocates that Li₂O₂ decomposes to 2Li and O₂, further augmented by the densification in specific molar volumes.

• Research Organization: Washington State Univ., Pullman, WA (United States); Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division; USDHS Science and Technology Directorate (S&T) Office of University Programs; Defense Threat Reduction Agency (DTRA); National Science Foundation (NSF)
• Contributing Organization: Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab., High Pressure Collaborative Access Team (HPCAT)
• Grant/Contract Number: NA0001974; 2013-ST-061-ED0001; HDTRA1-12-01-0020; 1203834; FG02-99ER45775
• OSTI ID: 1467875
• Journal Information: Journal of Chemical Physics, Vol. 145, Issue 8; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
raman spectra
high pressure
rietveld refinement
phase transitions
lattice modes
x-ray diffraction
crystal structure
diamond anvil cells
lithium