Ferroelastic n-heptylammonium dihydrogenarsenate.
n-Heptylammonium dihydrogenarsenate, (C(7)H(18)N)[As(O)(2)(OH)(2)] (C7ADA), is ferroelastic at room temperature and isostructural with n-heptylammonium dihydrogenphosphate (C7ADP). In contrast to the other known n-alkylammonium dihydrogenphosphates (CnADP) and dihydrogenarsenates (CnADA), two independent anions in the present structure are substantially disordered ( approximately 88 and approximately 12%, respectively). There are strong hydrogen bonds between the dihydrogenarsenates themselves, and moderate hydrogen bonds between the dihydrogenarsenates and the n-alkylammonium groups. The hydrogen-bond distances correspond well to those observed in the dihydrogenphosphates. There are two H atoms in the structure which are involved in asymmetric hydrogen bonds between respective oxygen pairs. These H atoms jump from the donor to the acceptor O atoms during ferroelastic switching.
Fábry
J
J
Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 180 40 Prague 8, Czech Republic. fabry@fzu.cz
Krupková
R
R
Císarová
I
I