Structure and bonding features of Ae6Mg7H26 (Ae = Sr, Ba) with complex polyhedrons: First-principles calculations

Structure and bonding features of hydride Ae6Mg7H26 (Ae = Sr, Ba) were investigated by first principles calculations. The Ba–H distance in Ba6Mg7H26 is longer relative to the Sr–H in Sr6Mg7H26, while the Ba-containing polyhedron with higher symmetry and high coordination numbers possesses high stability reflected by the more negative formation enthalpy obtained for Ba6Mg7H26. Hydrogen release from Sr6Mg7H26 would be easier. The electronic structures indicate that the Ae6Mg7H26 (Ae = Sr, Ba) exhibits non-metallic properties and the valence band is primarily dominated by H–s electrons. The chemical bonds in Ae6Mg7H26 (Ae = Sr, Ba) exhibit primary covalent feature with definite ionic component, the covalent feature of Ba–H is more obvious than that of Sr–H. These electronic structures reveal the underlying mechanism for structure and bonding features of the hydride Ae6Mg7H26 (Ae = Sr, Ba).