title: M(m)H(n)(XO4)((m+n)/2) crystals: structure, phase transitions, hydrogen bonds, conductivity. I. K9H7(SO4)8·H2O crystals--a new representative of the family of solid acid conductors.
abstract: To reveal the structural conditionality for anomalies in physical properties, including dielectric and optical properties, diffraction studies of K9H7(SO4)8·H2O crystals were performed using synchrotron radiation in the temperature range 293-450 K and determined at 405 K, taking H atoms into account. The results indicate that the occurrence of high conductivity in K9H7(SO4)8·H2O crystals with a temperature increase is associated with the outward diffusion of water molecules, hydrogen-bond network rearrangement and the formation of channels for the possible motion of K(+) ions. A rearranged system of hydrogen bonds consists of permanent bonds and partly of dynamically disordered bonds. Hydrogen-bond rearrangement and the hindered back diffusion of water to the crystal bulk stabilize the high-temperature crystal structure right down to room temperature.
authors.affiliation: Institute of Crystallography RAS, Leninsky pr. 59, 119333 Moscow, Russian Federation.
authors.forename: Irina
authors.initials: I
authors.lastname: Makarova
authors.affiliation: Institute of Crystallography RAS, Leninsky pr. 59, 119333 Moscow, Russian Federation.
authors.forename: Vadim
authors.initials: V
authors.lastname: Grebenev
authors.affiliation: Institute of Crystallography RAS, Leninsky pr. 59, 119333 Moscow, Russian Federation.
authors.forename: Elena
authors.initials: E
authors.lastname: Dmitricheva
authors.affiliation: Institute of Crystallography RAS, Leninsky pr. 59, 119333 Moscow, Russian Federation.
authors.forename: Valentina
authors.initials: V
authors.lastname: Dolbinina
authors.affiliation: Swiss-Norwegian Beam Lines at European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, 38000 Grenoble, France.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Chernyshov
keywords: X-ray analysis; high temperature; hydrogen bonds; superionic transitions