title: Raman investigation on the behavior of parasibirskite CaHBO3at high pressure.
abstract: Knowledge about the stability of hydrous borates and borosilicates at high pressures are of critical importance to our understanding on the boron geochemical cycle. Raman spectroscopic measurements of parasibirskite CaHBO3, containing the [BO2(OH)] groups, have been made to pressures up to 5.4GPa. The Raman data show that a progressive structural evolution from ambient pressure to 5.4GPa can be accounted for by the same monoclinic phase P21/m, where the splitting of several Raman bands observed at some pressures is interpreted as the effect of the complex disordering in the H-bond network that has bifurcated H-bonds and ½-occupied H sites. There is no unambiguous evidence for phase transition to the ordered P21monoclinic phase predicted by first-principles calculations at T=0K (W. Sun et al., Can. Miner., 2011). On the contrary, the disordering of parasibirskite, evidenced by the widening and attenuating Raman spectra, increases markedly at high pressures above 4.5GPa that results in incipient amorphization. Comparison of theoretical (lattice-dynamical) and experimental Raman spectra allows the reliable interpretation of almost all observed bands. The strongest symmetric B-O stretching band v1at the wavenumber 908cm-1, which is split into a doublet at high pressures, exhibits a shift rate of 4.22cm-1/GPa for the main component.
authors: V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Pr. Acad. Koptyug 3, Novosibirsk 630090, Russia. Electronic address: svg@igm.nsc.ru.
authors: S V
authors: SV
authors: Goryainov
authors: Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada.
authors: Y
authors: Y
authors: Pan
authors: Fock Institute of Physics, St.-Petersburg State University, 199034 St.-Petersburg, Russia.
authors: M B
authors: MB
authors: Smirnov
authors: Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada.
authors: W
authors: W
authors: Sun
authors: Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005, Fujian Province, People's Republic of China.
authors: J-X
authors: JX
authors: Mi
keywords: High pressure; Hydrous borate; Isolated [BO(2)(OH)]; Lattice-dynamics; Parasibirskite; Raman spectra