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Title: Effects of pressure on the structure and lattice dynamics of ammonium perchlorate: A combined experimental and theoretical study

In this paper, ammonium perchlorate NH 4ClO 4 (AP) was studied using synchrotron angle-dispersive X-ray powder diffraction (XRPD) and Raman spectroscopy. A diamond-anvil cell was used to compress AP up to 50 GPa at room temperature (RT). Density functional theory (DFT) calculations were performed to provide further insight and comparison to the experimental data. A high-pressure barite-type structure (Phase II) forms at ≈4 GPa and appears stable up to 40 GPa. Refined atomic coordinates for Phase II are provided, and details for the Phase I → II transition mechanics are outlined. Pressure-dependent enthalpies computed for DFT-optimized crystal structures confirm the Phase I → II transition sequence, and the interpolated transition pressure is in excellent agreement with the experiment. Evidence for additional (underlying) structural modifications include a marked decrease in the Phase II b'-axis compressibility starting at 15 GPa and an unambiguous stress relaxation in the normalized stress-strain response at 36 GPa. Above 47 GPa, XRD Bragg peaks begin to decrease in amplitude and broaden. The apparent loss of crystalline long-range order likely signals the onset of amorphization. Three isostructural modifications were discovered within Phase II via Raman spectroscopy. Finally, a revised RT isothermal phase diagram is discussed based on themore » findings of this study.« less
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physical and Life Sciences Directorate
  2. Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
Publication Date:
Report Number(s):
Journal ID: ISSN 0021-9606; 931177
Grant/Contract Number:
AC52-07NA27344; AC02-06CH11357; AC02-05CH11231; FG02-94ER14466; EAR-1634415; EAR-1606856
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 149; Journal Issue: 3; Journal ID: ISSN 0021-9606
American Institute of Physics (AIP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Chicago, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
36 MATERIALS SCIENCE; phase transitions; synchrotrons; density functional theory; ionizing radiation; enthalpy; inorganic compounds; wave mechanics; Raman spectroscopy
OSTI Identifier: