Ferroelastic n-propylammonium dihydrogenphosphate

n-Propylammonium dihydrogenphosphate, C3H7NH3+.-H2PO4-, crystals are ferroe lastic at room temperature. The phase transition into the prototypic phase takes place at approximately 378 K. All atoms except two H atoms are 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 asymm etric hydrogen bond between an oxygen pair. Ferroelastic switching is conco mitant with jumps of these H atoms from the donor to the acceptor O atoms. The compound belongs to the structural family of n-alkylammonium dihydrogen phosphate and in particular to the structure type of pentylammonium dihydro genphosphate, which differs by localization of alternating layers from the rest of the known alkylammonium dihydrogenphosphates. The crystal was sligh tly twinned; the proportion of the minor domain was approximately 3.5%.