Pressure-induced chemical decomposition and structural changes of boric acid.
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.
Kuznetsov
Alexei Yu
AY
Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany. Alexei.Kuznetsov@uni-bayreuth.de
Pereira
Altair S
AS
Shiryaev
Andrei A
AA
Haines
Julien
J
Dubrovinsky
Leonid
L
Dmitriev
Vladimir
V
Pattison
Phil
P
Guignot
Nicolas
N