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Ferroelastic n-heptylammonium dihydrogenarsenate
J Fábry1, R Krupková, I Císarová
1Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 180 40 Prague 8, Czech Republic. fabry@fzu.cz
Summary
n-Heptylammonium dihydrogenarsenate (C7ADA) exhibits ferroelasticity and structural similarities to its phosphate counterpart. Its disordered anions and hydrogen bonding dynamics are key to its ferroelastic switching behavior.
Area of Science:
- Solid-state chemistry
- Crystallography
- Ferroelastic materials
Background:
- n-Alkylammonium dihydrogenarsenates (CnADA) and dihydrogenphosphates (CnADP) are known ferroelastic compounds.
- Understanding the structural and bonding characteristics is crucial for explaining ferroelasticity.
Purpose of the Study:
- To investigate the crystal structure and ferroelastic properties of n-heptylammonium dihydrogenarsenate (C7ADA).
- To elucidate the role of anion disorder and hydrogen bonding in the ferroelastic switching mechanism.
Main Methods:
- Single-crystal X-ray diffraction analysis.
- Structural comparison with related n-alkylammonium salts.
Main Results:
- C7ADA is ferroelastic at room temperature and isostructural with n-heptylammonium dihydrogenphosphate (C7ADP).
- Two independent arsenate anions exhibit significant disorder (approx. 88% and 12%).
- Strong arsenate-arsenate and moderate arsenate-ammonium hydrogen bonds were observed, similar to phosphates, with two H atoms involved in asymmetric hydrogen bonds facilitating ferroelastic switching.
Conclusions:
- The ferroelastic behavior of C7ADA is strongly influenced by anion disorder and hydrogen bonding dynamics.
- Proton transfer during ferroelastic switching is facilitated by asymmetric hydrogen bonds between arsenate groups.