title: Isostructural phase transition in m-carboxyphenylammonium monohydrogenphosphite.
abstract: Crystals of m-carboxyphenylammonium monohydrogenphosphite, C7H8NO2+.H2PO3- (m-CPAMP), space group P2(1)/c, grown from aqueous solution undergo a reversible first-order single-crystal phase transition at Tc = 246 (2) K with a hysteresis of 3.6 K. The thermal behaviour of the sample was characterized by differential scanning calorimetry (DSC) experiments. Variations of the unit-cell parameters versus temperature between 100 and 320 K are reported. The transition from the higher-temperature phase (HTP) to the lower-temperature phase (LTP) is characterized by a unit-cell volume contraction of 1.77%. The average structure and unit-cell packing of m-CPAMP at lower temperature (100 K) are reported from accurate X-ray data sets and compared with those of the higher-temperature phase (293 K) in order to investigate the mechanism of the phase transition. The reciprocal lattice reconstruction showed a few very weak satellite reflections which will be discussed in a forthcoming paper.
authors.affiliation: Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques LCM3B CNRS UMR 7036, Université Henri Poincaré, Nancy 1, Faculté des Sciences, BP 239, 54506 Vandoeuvre-lès-Nancy CEDEX, France.
authors.forename: El Eulmi
authors.initials: el E
authors.lastname: Bendeif
authors.forename: Slimane
authors.initials: S
authors.lastname: Dahaoui
authors.forename: Michel
authors.initials: M
authors.lastname: François
authors.forename: Nourredine
authors.initials: N
authors.lastname: Benali-Cherif
authors.forename: Claude
authors.initials: C
authors.lastname: Lecomte