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Vibrational entropy of disordering in omphacite.

ABSTRACT: The cations of an ordered omphacite from the Tauern window were gradually disordered in piston cylinder experiments at temperatures between 850 and 1150 °C. The samples were examined by X-ray powder diffraction and then investigated using low-temperature calorimetry and IR spectroscopy. The low-temperature heat capacity data were used to obtain the vibrational entropies, and the line broadening of the IR spectra served as a tool to investigate the disordering enthalpy. These data were then used to calculate the configurational entropy as a function of temperature. The vibrational entropy does not change during the cation ordering phase transition from space group C2/c to P2/n at 865 °C but increases with a further temperature increase due to the reduction of short-range order.

Supplementary information

The online version contains supplementary material available at 10.1007/s00269-023-01260-7.

SUBMITTER: Benisek A

PROVIDER: S-EPMC10682307 | biostudies-literature | 2023

REPOSITORIES: biostudies-literature

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Vibrational entropy of disordering in omphacite.

Benisek Artur A Dachs Edgar E Carpenter Michael A MA Joachim-Mrosko Bastian B Vielreicher Noreen M NM Wildner Manfred M

Physics and chemistry of minerals 20231127 4

The cations of an ordered omphacite from the Tauern window were gradually disordered in piston cylinder experiments at temperatures between 850 and 1150 °C. The samples were examined by X-ray powder diffraction and then investigated using low-temperature calorimetry and IR spectroscopy. The low-temperature heat capacity data were used to obtain the vibrational entropies, and the line broadening of the IR spectra served as a tool to investigate the disordering enthalpy. These data were then used ...[more]

PMID: 38037626

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