Structure and bonding features of Ae_6Mg_7H_(26) (Ae = Sr, Ba) with complex polyhedrons:First-principles calculations

摘要

Structure and bonding features of hydride Ae_6Mg_7H_(26) (Ae = Sr, Ba) were investigated by first principles calculations. The Ba-H distance in Ba_6Mg_7H_(26) is longer relative to the Sr-H in Sr_6Mg_7H_(26), while the Ba-containing polyhedron with higher symmetry and high coordination numbers possesses high stability reflected by the more negative formation enthalpy obtained for Ba_6Mg_7H_(26). Hydrogen release from Sr_(6-) Mg_7H_(26) would be easier. The electronic structures indicate that the Ae_6Mg_7H_(26) (Ae = Sr, Ba) exhibits non-metallic properties and the valence band is primarily dominated by H-s electrons. The chemical bonds in Ae_6Mg_7H_(26) (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 Ae_6Mg_7H_(26) (Ae = Sr, Ba).