Study on Soft Phonons and Mode Grüneisen Parameters in a Framework Material H3[Co(CN)6]

The author has spent the last several years researching phonons and their structure-properties relationships in a variety of advanced functional materials, including graphene, TiS3 nanosheet and nanofiber, VSe2 nanosheet, and SnO2 nanoparticles, as well as recently established low-dimensional 2D materials such as graphene, TiS3 nanosheet and nanofiber, VSe2 nanosheet, and SnO2 nanoparticles. The phonons and mode Grüneisen parameters of a flexible framework compound H3[Co(CN)6] are described in detail in this book chapter. H3[Co(CN)6] is a cyanide with a flexible framework structure and negative thermal expansion along the c-axis. Under hydrostatic pressure ranging from ambient to 11 GPa, in-situ high-pressure Raman spectroscopy experiments on H3[Co(CN)6] in a diamond-anvil cell were carried out. A phase transition from trigonal to monoclinic is identified at 2.3 GPa based on the evolution of Raman spectra, band splitting, and discontinuous changes in the pressure dependence of band frequencies. A lattice band at 140 cm-1 and the Co-CN deformation band at 348 cm-1, in contrast to other bands, softened with increasing pressure. The pressure dependence of Raman mode frequencies (d/dP) were used to calculate mode Grüneisen parameters (yi) for the ambient trigonal phase. As the molecule amorphized about 11 GPa, there was no Raman band with a flat spectral characteristic.

Author(S) Details

K. K. Mishra
Department of Physics, University of Puerto Rico, San Juan, PR 00925-2537, USA.

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