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.

The novel compound WAl2 is the first aluminide crystallizing with the CrSi2 structure type. This compound is stable up to high pressures of at least 31.5 GPa. The chemical bonding analysis by means of the electron localization function (ELF) reveals a partially covalent bonding being responsible for the anisotropic compression behavior.Figure optionsDownload as PowerPoint slide