Repository logo

Vibrational entropy of disordering in omphacite.

Published version

Repository DOI

Change log


Benisek, Artur 
Dachs, Edgar 
Carpenter, Michael A 
Joachim-Mrosko, Bastian 
Vielreicher, Noreen M 


UNLABELLED: 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.


Acknowledgements: This work was supported by grants from the Austrian Science Fund (FWF), project number P33904, which is gratefully acknowledged. We thank G. Tippelt for performing the X-ray experiments and E. Forsthofer for maintaining the Materials Studio software at the Salzburg University. We also thank two anonymous reviewers for their detailed and constructive comments.

Funder: Paris Lodron University of Salzburg


Autocorrelation, Calorimetry, Density functional theory, Disorder, Enthalpy, Entropy, IR spectroscopy, Line broadening, Omphacite, Order, Pyroxene

Journal Title

Phys Chem Miner

Conference Name

Journal ISSN


Volume Title



Springer Science and Business Media LLC
Austrian Science Fund (P33904, P33904)