Crystal structure and high-pressure studies of WAl2, an aluminide crystallizing with the CrSi2 structure type

The novel intermetallic compound WAl₂ crystallizes with space group P6₄22 and lattice parameters a=4.7422(1) Å, c=6.6057(2) Å. The crystal structure was solved from single-crystal X-ray diffraction data. WAl₂ was found to be the first aluminide that is isotypic with CrSi₂. A high-pressure powder X-ray diffraction study showed its stability up to at least 31.5(1) GPa. The bulk modulus was calculated by fitting a third-order Birch-Murnaghan equation of state to the pressure-volume data as K₀=168(11) GPa and its pressure derivative K′=7.7(1.0). Partially covalent bonding between W and Al atoms was indicated by means of the electron localization function (ELF) and explains the anisotropic compression behavior. Quantum chemical calculations identify WAl₂ as a potential high-temperature phase.