Crystal structure of KAlH4 from first principle calculations

The crystal structure of KAlH4 is determined by the first principle projected augmented plane wave method taking different possible structural arrangements into consideration. From the total energy it is concluded that KAlH4 crystallizes in the orthorhombic KGaH4-type structure (space group Pnma) with unit-cell dimensions a = 9.009, b = 5.767, c = 7.399 Angstrom. A metastable modification with alpha-NaAlH4-type structure is predicted in energetic close proximity to the stable phase. The electronic structure shows that KAlH4 has a non-metallic character with a band gap of approximately 5.5eV. (C) 2003 Elsevier B.V. All rights reserved.