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Thermodynamic Tuning of Calcium Hydride by Fluorine Substitution

Published online by Cambridge University Press:  22 May 2012

Eugenio R. Pinatel ,
Line H. Rude ,
Marta Corno ,
Maria Kragelund ,
Piero Ugliengo ,
Torben R. Jensen  and
Marcello Baricco
Eugenio R. Pinatel
Affiliation:
Dipartimento di Chimica and NIS, Università di Torino, Via P. Giuria 7/9, 10125, Torino, Italy
Line H. Rude
Affiliation:
Center for Materials Crystallography, Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
Marta Corno
Affiliation:
Dipartimento di Chimica and NIS, Università di Torino, Via P. Giuria 7/9, 10125, Torino, Italy
Maria Kragelund
Affiliation:
Center for Materials Crystallography, Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
Piero Ugliengo
Affiliation:
Dipartimento di Chimica and NIS, Università di Torino, Via P. Giuria 7/9, 10125, Torino, Italy
Torben R. Jensen
Affiliation:
Center for Materials Crystallography, Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
Marcello Baricco
Affiliation:
Dipartimento di Chimica and NIS, Università di Torino, Via P. Giuria 7/9, 10125, Torino, Italy
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Abstract

Fluorine substitution in CaH2 has been studied by means of experimental and theoretical methods. Samples with various compositions have been prepared by ball milling. In situ X-ray diffraction analysis has been carried out as a function of temperature by synchrotron radiation experiments. An increase of mixing has been observed during heating, suggesting that mixing is thermodynamically favoured but it is kinetically hindered at low temperatures. Ab initio DFT calculations have been performed to estimate the thermodynamic mixing properties of both orthorhombic and cubic solid solutions. On the basis of ab initio results and literature information, a thermodynamic assessment within the CALPHAD framework has been performed and the pseudo binary CaH2-CaF2 phase diagram has been calculated. The formation of orthorhombic and cubic terminal solid solutions in the CaH2-CaF2 system is predicted, in good agreement with experimental findings.

Keywords

CaHchemical substitution
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1441: Symposium P – Advanced Materials and Nanoframeworks for Hydrogen Storage and Carbon Capture , 2012 , mrss12-1441-p05-16
Copyright
Copyright © Materials Research Society 2012

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References

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