Hi, I am doing a phenix.fmodel calculation for a PDB structure containing anisotroipc B. If I understand it correctly, the B factor is composed of both the isotropic B for ATOM line (Biso) and the anisotropic B from ANISOU line (Uani): Fc=sigma ( fi * exp (-Biso*s*s) * exp (-st*Uani*s) * exp (i*r*s) ) Please correct me if the above equation is wrong. I also noticed that in PDB, the Uani (after scaling by 10^-4) is generally much smaller than Biso. So I assume that Biso has a much bigger contribution than Uani, the latter only implying the vibrational anisotropicity. However, I did a test calculation by setting all Bio to 0 whereas keeping Uani unchanged. Due to the above assumption, I expected the results should be very different from the native structure; however, coot told me they were just so close... Maybe I am wrong somewhere... Best Regards, Hailiang