Low-frequency lattice vibrations from atomic displacement parameters of α-FOX-7, a high energy density material

Thammarat Aree, Charles J. McMonagle, Adam A. L. Michalchuk, Dmitry Chernyshov

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Abstract

Highly anharmonic thermal vibrations may serve as a source of structural instabilities resulting in phase transitions, chemical reactions and even the mechanical disintegration of a material. Ab initio calculations model thermal motion within a harmonic or sometimes quasi-harmonic approximation and must be com plimented by experimental data on tem per ature-dependent vibrational frequencies. Here multi-tem per ature atomic displacement parameters (ADPs), derived from a single-crystal synchrotron diffraction experiment, are used to characterize low-frequency lattice vibrations in the α-FOX-7 layered structure. It is shown that despite the limited quality of the data, the extracted frequencies are reasonably close to those derived from inelastic scattering, Raman measurements and density functional theory (DFT) calculations. Vibrational anharmonicity is parameterized by the Grüneisen parameters, which are found to be very different for in-layer and out-of-layer vibrations.

Original languageEnglish
Pages (from-to)376-384
Number of pages9
JournalActa Crystallographica Section B Structural Science, Crystal Engineering and Materials
Volume78
Issue number3
DOIs
Publication statusPublished - 30 Jun 2022

Keywords

  • ADPs
  • Anisotropic atomic displacement parameters
  • Crystal dynamics
  • Normal mode analysis
  • α-FOX-7

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Metals and Alloys
  • Materials Chemistry

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