Thermodynamic modelling of Mg(BH4)2

• DFT calculations providing missing thermodynamic data for Mg(BH4)2were performed.
• A Calphad assessment of Mg(BH4)2 was performed, considering all the available data.
• Stable and metastable phase diagrams have been calculated for Mg(BH4)2.
• Several dehydrogenation paths of Mg(BH4)2 have been analysed and discussed.

Application of the Calphad method to the description of thermodynamic properties in complex borohydride-based systems may allow a faster development of hydrogen storage materials. It is, however, limited by the low number of available thermodynamic description for borohydrides in thermodynamic databases. In the present work, a Calphad assessment of Mg(BH4)2 has been performed, considering available thermodynamic data. DFT calculations have been performed in order to provide missing thermodynamic data and to calculate the relative stability of the α, β and γ polymorphs. Experimental results have been compared detecting inconsistencies between them.The database obtained has been used to estimate driving forces for several dehydrogenation reactions. The dehydrogenation reaction leading to the formation of MgB2 and gaseous hydrogen is the most favoured thermodynamically, even if at low temperatures the formation of MgB12H12 is competitive. On the contrary, positive driving forces have been calculated for the decomposition into B2H6 and Mg(B3H8)2.