Figure 1

(a) The atomic arrangement of WSe₂ in perspective and side views. W is represented by pink balls and Se by blue balls. a and c are cell parameters. θ is Se-W-Se bond angle and d_W − Se is W-Se bond length. (b) The XRD pattern of WSe₂ at ambient conditions. Inset: a piece of WSe₂ single crystal. (c) Representative synchrotron X-ray diffraction patterns of WSe₂ during the compression and decompression (by d) runs (λ = 0.4246 Å). The observed and Rietveld refined profiles at 1.8 GPa is shown. The open circles and red lines are the experimental and calculated data. The positions of the Bragg reflections are marked by vertical sticks. The refined value is R_P = 1.05% with weighted profile R_WP = 1.40%.