Fig. 4.

High-pressure synchrotron X-ray diffraction. a SXRD patterns of (Li_1−xFe_x)OHFe_1−ySe fitted with LeBail method. The first and second rows of tick marks in a represent the Bragg positions of the tetragonal P4/nmm phase of (Li_1−xFe_x)OHFe_1−ySe and the secondary phase Se with space group P3₁21. b–d Pressure dependence of unit-cell parameters a, c, V, and the c/a ratio. The solid line in d is the Birch–Murnaghan fitting curve used to extract the bulk modulus given in the inset