European Synchrotron Radiation Facility, 6 rue Jules Horowitz, B. P. 220, F-38043, Grenoble cedex, France.
Published: May 2010
AI Article Synopsis
Article Abstract
We have performed in situ X-ray diffraction, Raman scattering, pseudosymmetry analysis and quantum mechanical atomistic simulations of the structure and behaviour of LaF(3) at high pressure, up to and exceeding the phase transition pressure reported for the I4/mmm structure and Cmma symmetry proposed previously. We observe that the structure of LaF(3)-II is best described as being of anti-Cu(3)Ti-type (oP8, Pmmn, SG59), which is closely related to the I4/mmm structure obtained by simulation, through notional distortion, and is evidently similar to the Cmma symmetry by comparison of published diffraction data. We demonstrate that the models are also related to each other, and can be derived through pseudosymmetry searches. LaF(3)-II does not undergo further phase transitions before at least 60 GPa, and none are expected before 1 Mbar. The similarity between the anti-Cu(3)Ti-type and the I4/mmm structure models and our in situ diffraction data, supports the transition mechanisms derived from atomistic model simulations for a generic REF(3) transition to the post-tysonite phase (where RE = La, Ce, Pr, Nd).
Crystalline Ba(CH) was obtained by the reaction of elemental barium dissolved in liquid ammonia, forming a blue electride, and acetylene (CH) injected into the reaction vial with the electride solution. From the colorless precipitate that was obtained after evaporation of the ammonia, the crystal structure of Ba(CH) was solved and refined using synchrotron powder diffraction data. It crystallizes in the trigonal space group 3̅1 (no.
Based on density functional theory and evolutionary algorithms the thermodynamically stable structures of MnN and their stability - fields were revealed in the pressure range of 0-50 GPa. The MnN-4̄3 polymorph (zinc blende-type) was shown to be the ambient pressure phase, while experimentally known MnN-4/ (distorted NaCl-type) is a high-temperature phase quenchable to the ambient condition. At 5.
YOsB (x = 1.161) crystallizes as a tetragonal incommensurate composite of columns of Y atoms extending along [001] in an OsB framework. The structure was refined using the superspace approach.
Sodium and potassium have been doped into LaSrCuO to form La Sr K Na CuO solid solutions by a solid-state reaction, which crystallizes in the 4/ space group when 0 ≤ < 0.16 and when 0.16 < ≤ 0.
The high-pressure study on zirconium disulfide (ZrS) has been conducted up to ∼33.9 GPa by using synchrotron X-ray diffraction at room temperature and electrical transport measurements, aiming to investigate the pressure-induced structural phase transitions and the metallization of the material. The experiments indicated that a progressive structural evolution occurs as the sequence below: hexagonal (space group (SG): 3̅) → monoclinic (SG: ) started at 2.
