We present a structure model for constructing $\text{Mg}{\left({\text{BH}}_4\right)}_2$. The first-principles calculations reveal that some stable ground-state crystal structures of $\text{Mg}{\left({\text{BH}}_4\right)}_2$ have the same or slightly lower energy than the $I\text{−}4m2$ structure predicted in a paper by Ozolins et al. [Phys. Rev. Lett. 100, 135501 (2008)]. The possible mechanism for the anomalous stability originates from the fact that the charge transfer between different atoms is more homogeneous. The structure model can be anticipated to have potential application for predicting new stable structures of this group of homologous materials.

• Received 9 February 2009

DOI:https://doi.org/10.1103/PhysRevB.79.212102