Transformation pathways and isothermal compressibility of a MTN-type clathrasil using penetrating and non-penetrating fluids

Autor(en)
Katharina Sarah Scheidl, Herta Silvia Effenberger, Takehiko Yagi, Koichi Momma, Ronald Miletich
Abstrakt

The high-pressure behavior of the natural MTN-type clathrasil chibaite was investigated with in situ single crystal X-ray diffraction and Raman spectroscopy under hydrostatic pressures up to 10.3 GPa. The experiments were conducted in diamond-anvil cells using 4:1 methanol-ethanol mixture (ME), helium (He) and neon (Ne) as pressure-transmitting media. The pressure dependent unit-cell volumes of the room-pressure polymorph yield an isothermal bulk modulus K-T0 = 25.75 (19) GPa for the compression in the non-penetrating ME fluid. Due to the penetration of the Ne and He atoms into the cages of the framework, the crystal structure is significantly stiffened resulting in K-T0 = 42.5 (1.2) GPa (Ne) and K-T0 = 58 (2) GPa (He). Under the influence of pressure both the evolution of the Raman spectra and the change in cell metrics indicate a distortion of the lattice without leading to a complete pressure-induced amorphization, as observed for many comparable porous structures. Compressed in the non-penetrating ME, the cubic Fd (3) over barm framework of chibaite undergoes a first transformation step in the pressure range between L7 GPa and 2.2 GPa and a second one between 3.9 GPa and 4.3 GPa. The accompanied formation of crystal domains did not allow a reliable determination of the distorted crystal structures. The unit cell parameters might suggest a monoclinic metric for pressures > 1.7 GPa and a monoclinic or tetragonal metric for pressures > 3.9 GPa. However, in some samples even the co-existence of crystal domains of a different degree of lattice distortions has been proved.

Organisation(en)
Institut für Mineralogie und Kristallographie
Externe Organisation(en)
University of Tokyo, National Museum of Nature and Science
Journal
Microporous and Mesoporous Materials
Band
273
Seiten
73-89
Anzahl der Seiten
17
ISSN
1387-1811
DOI
https://doi.org/10.1016/j.micromeso.2018.06.033
Publikationsdatum
01-2019
Peer-reviewed
Ja
ÖFOS 2012
104026 Spektroskopie, 104011 Materialchemie, 105113 Kristallographie
Schlagwörter
ASJC Scopus Sachgebiete
Condensed Matter Physics, Mechanics of Materials, Chemistry(all), Materials Science(all)
Link zum Portal
https://ucris.univie.ac.at/portal/de/publications/transformation-pathways-and-isothermal-compressibility-of-a-mtntype-clathrasil-using-penetrating-and-nonpenetrating-fluids(f28e987a-8913-42de-93e9-0589bacf0862).html