Facilities of the High Pressure Collaborative Access Team (HPCAT) at beamline sector 16-ID-B of the Advanced Photon Source (APS) were used to perform the synchrotron experiments. The Mo 2-x W x BC samples were incrementally compressed to ∼55-60 GPa in steps of 1-5 GPa at ambient temperature. At each step, monochromatic X-rays (λ = 0.4066 Å) and a Pilatus detector were used to collect angle-dispersive diffraction spectra in axial geometry. X-ray energy was ∼30.5 keV and the beam was focused to 5 µm × 4 µm. A cerium dioxide standard was used to calibrate sample-to-detector distance (209.7 mm), detector tilt, and detector rotation. Collected 2D diffraction images were converted from polar coordinates to Cartesian coordinates using FIT2D. Lattice parameters were determined from the diffraction data using the Le Bail method as implemented in the MAUD (Materials Analysis Using Diffraction) software package. Because near-hydrostatic conditions were maintained, lattice strain was not refined. An isothermal, third-order Birch-Murnaghan EOS (Equation ) was fit to the relative cell volume versus pressure curves using EOSFit software to determine K 0 and the first pressure derivative of the bulk modulus, K 0 . 24