Raman spectroscopy and X‐ray diffraction of pressure‐induced reversible structure change in K₂OsO₂(OH)₄

Abstract

High‐pressure structural evolution of K2OsO2(OH)4, a potassium osmate dihydrate, has been studied by high‐pressure Raman spectroscopy and angle dispersive X‐ray diffraction. A pressure‐induced reversible structure change is observed at approximately 8 GPa, evidenced by the splitting of Raman modes and the addition of X‐ray diffraction peaks. The splitting of phonon generally occurs in the Raman modes with smaller Grüneisen parameters. The pressure‐induced structural change is correlated with the relatively isolated arrangement of Os–O polyhedron. In addition, the zero‐pressure bulk modulus B0 = 46(1) GPa and zero‐pressure Grüneisen parameters γ of K2OsO2(OH)4 are given and discussed.

High‐pressure studies of Mn2(C2H6N6)4(NO3)4·2H2O by Raman scattering, infrared absorption, and synchrotron X‐ray diffraction

“…Raman external modes in the spectral range of 0–400 cm −1 are sensitive to pressure that can be used as an indication of structural changes 36,37 . At 0.5 GPa, the new Raman external modes appeared at 68, 109, and 379 cm −1 labeled as letter N, and another Raman external mode disappeared at 253 cm −1 marked by a down arrow, as depicted in Figure 3A.…”

“…Raman external modes in the spectral range of 0-400 cm À1 are sensitive to pressure that can be used as an indication of structural changes. 36,37 external modes indicate the first phase transition of Mn, which transformed from phase I to phase II. The vibrational modes in the spectral range of 400-4000 cm À1 are the Raman internal modes.…”

Raman spectroscopy and X‐ray diffraction of diphenylphosphoryl azide under high pressures

“…These changes imply that DPPA underwent a phase transition from Phase I to Phase II. [38,39] The new Raman peak is assigned to N 3 stretching mode (ν N 3 ) as marked by asterisk (*), and the disappeared Raman peaks are the overtones of the N 3 asymmetric stretching mode (2ν as N 3 ) as labeled with diamonds (♦). These variations of vibration modes of the azide group suggested the change of molecular conformation, leading to the first phase transition of DPPA.…”