Structural Evolution Leading to the Thermosalient Phase Transition of Oxitropium Bromide

Klaser, Teodoro; Popović, Jasminka; Lončarić, Ivor; Skoko, Željko (2025) Structural Evolution Leading to the Thermosalient Phase Transition of Oxitropium Bromide. Molecules, 30 (5). ISSN 1420-3049

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Official URL: http://doi.org/10.3390/molecules30051107

Abstract

This study investigates the thermosalient effect in oxitropium bromide, with a focus on the role of anisotropic thermal expansion, elastic properties, and sound propagation in driving this phenomenon. Variable-temperature X-ray powder diffraction (VTXRPD) revealed significant anisotropic thermal expansion, including negative thermal expansion (NTE) along the c-axis in the low-temperature Form A. Density functional theory (DFT) calculations were used to analyze elastic properties of oxitropium bromide and confirmed that it does not exhibit negative compressibility, emphasizing thermal anisotropy as the primary factor in the phase transition. Studies of elastic constants and sound propagation demonstrated a preferred pathway for energy transfer along the z-direction, enabling rapid strain release during the phase transition. These findings confirmed that the thermosalient effect arises from cooperative molecular motion, resulting in an abrupt and energetic transformation driven by the interplay of structural anisotropy and elastic properties.

Item Type:

Article

Uncontrolled Keywords:

thermosalient effect; phase transition; negative thermal expansion; thermal anisotropy; PXRD; DFT; oxitropium bromide

Subjects:

NATURAL SCIENCES > Physics
NATURAL SCIENCES > Chemistry

Divisions:

Division of Materials Physics
Theoretical Physics Division

Projects: