(color online) A fitting comparison between bcc (a) and rhombohedral (b) structures of niobium at 47 GPa. The circles are the integrated diffraction patterns of niobium and the solid lines are the calculated patterns. The short vertical lines label the 2θ location of diffraction peaks. The crystal structure, space group, fitting results, and lattice parameter α of the unit cell are shown in the right-upper panel. No resolved splitting peaks were observed at all pressures.