Structural, bonding and elastic properties of Mg(NH2BH3)2, Ca(NH2BH3)2 and Sr(NH2BH3)2

• Sr(NH2BH3)2 have more dispersion forces over Mg(NH2BH3)2 and Ca(NH2BH3)2.
• Alkaline-earth metal amidoboranes found to be wide band gap insulators.
• Mg(NH2BH3)2, Ca(NH2BH3)2 and Sr(NH2BH3)2 have strong covalent bonding.
• Alkaline-earth metal amidoboranes are found to be mechanically stable.
• Ca(NH2BH3)2 is less plastic than Mg(NH2BH3)2 and Sr(NH2BH3)2.

The structural, bonding and elastic properties of alkaline earth metal amidoboranes (Mg(NH2BH3)2, Ca(NH2BH3)2 and Sr(NH2BH3)2) have been studied using van der Waals (vdW) corrected first principles calculations. Interestingly Sr(NH2BH3)2 alone exhibit considerable vdW interactions effect to bind the crystal whereas it is less pronounced in the case of Mg(NH2BH3)2 and Ca(NH2BH3)2. Later, it is found that these are wide band gap insulators and the band gap values for Mg(NH2BH3)2, Ca(NH2BH3)2 and Sr(NH2BH3)2 are 4.78 eV, 3.87 eV and 3.88 eV, respectively. From the charge density distribution and bond population analysis, we conclude that there exists a strong covalent bond between B–H and N–H atoms. From the calculated elastic constants the alkaline-earth metal amidoboranes are found to be mechanically stable and Ca(NH2BH3)2 is found to be less plastic than Mg(NH2BH3)2 and Sr(NH2BH3)2.