First-principles calculations of the crystal structure, electronic structure, and thermodynamic stability of Be (BH4) 2

Abstract

Alanates and boranates are intensively studied because of their potential use as hydrogen storage materials. In this paper, we present a first-principles study of the electronic structure and the energetics of beryllium boranate [Be (BH4) 2]. From total energy calculations, we show that-in contrast to the other boranates and alanates-hydrogen desorption directly to the elements is likely and is at least competitive with desorption to the elemental hydride (BeH2). The formation enthalpy of Be (BH4) 2 is only -0.14 eV/ H2 (at T=0 K). This low value can be rationalized by the participation of all atoms in the covalent bonding, which is in contrast to the ionic bonding observed in other boranates. From calculations of thermodynamic properties at finite temperature, we estimate a decomposition temperature of 162 K at a pressure of 1 bar. © 2008 The American Physical Society.