title: Pressure-induced chemical decomposition and structural changes of boric acid.
abstract: A combined synchrotron X-ray diffraction, Raman scattering, and infrared spectroscopy study of the pressure-induced changes in H(3)BO(3) to 10 GPa revealed a new high-pressure phase transition between 1 and 2 GPa followed by chemical decomposition into cubic HBO(2), ice-VI, and ice- VII at approximately 2GPa. The layered triclinic structure of H(3)BO(3) exhibits a highly anisotropic compression with maximum compression along the c direction, accompanied by a strong reduction of the interlayer spacing. The large volume variation and structural changes accompanying the decomposition suggest high activation energy. This yields a slow reaction kinetics at room temperature and a phase composition that is highly dependent on the specific pressure-time path followed by the sample. The combined results have been used to propose a mechanism for pressure-induced dehydration of H(3)BO(3) that implies a proton disorder in the system.
authors.affiliation: Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany. Alexei.Kuznetsov@uni-bayreuth.de
authors.forename: Alexei Yu
authors.initials: AY
authors.lastname: Kuznetsov
authors.forename: Altair S
authors.initials: AS
authors.lastname: Pereira
authors.forename: Andrei A
authors.initials: AA
authors.lastname: Shiryaev
authors.forename: Julien
authors.initials: J
authors.lastname: Haines
authors.forename: Leonid
authors.initials: L
authors.lastname: Dubrovinsky
authors.forename: Vladimir
authors.initials: V
authors.lastname: Dmitriev
authors.forename: Phil
authors.initials: P
authors.lastname: Pattison
authors.forename: Nicolas
authors.initials: N
authors.lastname: Guignot