Fig. 2. Texture analysis of XRD data.

(A) Qualitative agreement between experimental image plates projected in 2θ-ϕ and a simulated diffraction pattern at P = 442(28) GPa. (Left, bottom axis) An averaged intensity lineout shows features consistent with both the B1 and B2 phases, and Ta calibrant at 1 bar. The red and green boxes represent simulated Laue diffraction locations from MgO B1 and uncompressed quartz [001] single crystals, respectively, from broadband x-ray thermal emission generated within the Cu He-α x-ray source plasma (see Materials and Methods). Also shown are Ta reference peaks (dashed green lines). (B) Our data are consistent with the WTM mechanism (26, 27), which is described in two steps: (left) sliding of atoms within alternate (001)_B1 layers in the [1$\overline{1}$0]_B1 direction (blue arrows along yellow plane) to unit cell denoted by black dashed-dot lines, followed by (center) an expansion in the [110]_B1 direction (vectors connecting atoms 1 to 8 and 2 to 7) and a uniform compression perpendicular to this direction, i.e., the [001]_B1 and the [1$\overline{1}$0]_B1 direction (atoms 3 to 6, 4 to 5, 1 to 2, and 8 to 7). The resulting [010]_B2 axis is orientated 45^° to [001]_B1. (right) The WTM mechanism results in (001)_B1 || ( $\overline{1}$01)_B2 and [1$\overline{1}$0]_B1 || [010]_B2 and produces six variants that can be detected in our experiments.