Low-compressibility of tungsten tetraboride: a high pressure X-ray diffraction study

Diamond anvil cell synchrotron X-ray diffraction (XRD) experiments have been carried out on submicron-sized tungsten tetraboride (WB4) at room temperature up to 50.8 GPa with a silicone oil pressure medium. The crystal structure of WB4 remains unchanged up to the highest pressure. The isothermal bulk modulus K 0 and its pressure derivative, , have been determined from the present compression by fitting the third-order Birch–Murnaghan equation of state: K 0=325±9 GPa and . The high value of the bulk modulus shows that WB4 has high stiffness and/or low-compressibility. Moreover, we also found that the compression behavior of the unit cell axes (a- and c-axes) of WB4 demonstrates an anisotropic nature of compressibility.