Structure, stability and superhalogen properties of sodium and magnesium borohydrides

► DFT calculations indicate superhalogen behavior for Na(BH4)2 and Mg(BH4)3. ► The electron affinity of Mg[Mg(BH4)3]3 is 6.18 eV and this is a hyperhalogen. ► The significant HOMO-LUMO gaps indicate very stable moieties.