Anionic substitution in hydrides The aim of anionic substitution in high capacity metal hydrides is to destabilize thermodynamic properties of the too stable pure compounds by substituting some of the H atoms with halogens. The nature of the halogen plays an important role in the resulting thermodynamic properties of the mixed compound. H/F substitution in simple hydrides First of all, a complete characterization of structural, vibrational and thermodynamic properties of Li, Na, Mg, Ca and Al pure hydride has been carried out in the DFT scheme, using a Gaussian localized basis set and the periodic ab initio CRYSTAL09 code [1]. Once chosen the reference methodology (a reliable and feasible set of computational parameters), calculations for the following solid state reaction (1-x)MHn + xMFn → MHn(1-x)Fnx were run and the mixed MHF compounds were carefully analyzed in terms of their properties. In the present contribution, the focus will be mainly on Li, Na and Ca cases, since it has been recently demonstrated that for Al [2] and Mg no mixed structures resulted. For these hydrides, promising results have been obtained, but relevant differences were found in the thermodynamics depending on the specific modelling approach. Considering Ca(H,F) as a test case, for both the cubic and orthorhombic phases, potential pitfalls will be highlighted, to establish a sensible choice of the computational strategy. References [1] R. Dovesi, V.R. Saunders, C. Roetti, R. Orlando, C.M. Zicovich-Wilson, F. Pascale, B. Civalleri, K. Doll, N.M. Harrison, I.J. Bush, P. D’Arco, M. Llunell, CRYSTAL09, University of Torino, Torino 2009 www.crystal.unito.it [2] J. E. Fonneløp, M. Corno, H. Grove, E. Pinatel, M. H. Sørby, P. Ugliengo, M. Baricco, B. C. Hauback, J. Alloy. Compd., 2010, doi: 10.1016/ j.jallcom.2010.08.147
First Principles Prediction of Structural, Vibrational and Thermodynamic Properties of Mixed Metal Hydrides and Fluorides
CORNO, MARTA;PINATEL, EUGENIO RICCARDO;UGLIENGO, Piero;BARICCO, Marcello
2011-01-01
Abstract
Anionic substitution in hydrides The aim of anionic substitution in high capacity metal hydrides is to destabilize thermodynamic properties of the too stable pure compounds by substituting some of the H atoms with halogens. The nature of the halogen plays an important role in the resulting thermodynamic properties of the mixed compound. H/F substitution in simple hydrides First of all, a complete characterization of structural, vibrational and thermodynamic properties of Li, Na, Mg, Ca and Al pure hydride has been carried out in the DFT scheme, using a Gaussian localized basis set and the periodic ab initio CRYSTAL09 code [1]. Once chosen the reference methodology (a reliable and feasible set of computational parameters), calculations for the following solid state reaction (1-x)MHn + xMFn → MHn(1-x)Fnx were run and the mixed MHF compounds were carefully analyzed in terms of their properties. In the present contribution, the focus will be mainly on Li, Na and Ca cases, since it has been recently demonstrated that for Al [2] and Mg no mixed structures resulted. For these hydrides, promising results have been obtained, but relevant differences were found in the thermodynamics depending on the specific modelling approach. Considering Ca(H,F) as a test case, for both the cubic and orthorhombic phases, potential pitfalls will be highlighted, to establish a sensible choice of the computational strategy. References [1] R. Dovesi, V.R. Saunders, C. Roetti, R. Orlando, C.M. Zicovich-Wilson, F. Pascale, B. Civalleri, K. Doll, N.M. Harrison, I.J. Bush, P. D’Arco, M. Llunell, CRYSTAL09, University of Torino, Torino 2009 www.crystal.unito.it [2] J. E. Fonneløp, M. Corno, H. Grove, E. Pinatel, M. H. Sørby, P. Ugliengo, M. Baricco, B. C. Hauback, J. Alloy. Compd., 2010, doi: 10.1016/ j.jallcom.2010.08.147
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