title: Ferroelastic n-butylammonium dihydrogenphosphate.
abstract: Crystals of n-butylammonium dihydrogenphosphate, C(4)H(9)NH(3)(+).H(2)PO(4)(-), reveal ferroelasticity at room temperature and a number of phase transitions when heated up to approximately 373 K. Some of these phase transitions show hysteresis effects. All atoms except two H atoms exist in pairs linked by the lost symmetry operations derived from the prototypic space group P2/b2(1)/n2(1)/a. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxygen pair. Ferroelastic switching is concomitant with jumps of these hydrogen species from donor to acceptor O atoms. The studied structure belongs to the structural family of n-hexyl- to n-decylammonium dihydrogenphosphates and differs by localization of alternating layers from n-propyl- and n-pentylammonium dihydrogenphosphates. The studied crystal was slightly twinned; the minor domain constituted approximately 2%.
authors.affiliation: Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 180 40 Praha 8, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Fábry
authors.forename: Ivana
authors.lastname: Císarová
authors.forename: Jan
authors.initials: J
authors.lastname: Kroupa