I want to calculate the octahedral rotation and octahedral tilt angle for my doped BiFeO3. The structure was confirmed using Rietveld Refinement through Fullprof Software. I obtain the Fe-O-Fe angles. using VESTA but Which formula I should used for calculating the tilt angle for monoclinic (Cc) unable to find. Also want to calculate the octahedral rotation angle. Can anyone help me?