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

Abstract

In this paper, ammonium perchlorate NH₄ClO₄ (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 the findings ofmore » this study.« less

Authors:

Kroonblawd, Matthew P. ^[1]; Koroglu, Batikan ^[1]; Zaug, Joseph M.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-8999-3800"
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Pagoria, Philip F. ^[1]; Goldman, Nir  ^[1];

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Greenberg, Eran  ^[2];

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Prakapenka, Vitali B. ^[2]; Kunz, Martin  ^[3];

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Bastea, Sorin ^[1]; Stavrou, Elissaios ^[1]

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+ Show Author Affiliations

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:

2018-07-18

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); National Science Foundation (NSF)

OSTI Identifier:

1465285

Report Number(s):

LLNL-JRNL-746751
Journal ID: ISSN 0021-9606; 931177

Grant/Contract Number:  

AC52-07NA27344; AC02-06CH11357; AC02-05CH11231; FG02-94ER14466; EAR-1634415; EAR-1606856

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 149; Journal Issue: 3; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; phase transitions; synchrotrons; density functional theory; ionizing radiation; enthalpy; inorganic compounds; wave mechanics; Raman spectroscopy