The xrefin optimize group statement optimizes grouped B-factors and occupancies, e.g., two for each residue. The procedure minimizes the function . The Powell conjugate gradient minimization method is used. B-factors and occupancies can be refined simultaneously by specifying both the B and the Q options.
Uniform shifts are applied
to the B-factors and occupancies for each of the selected
groups. The optimization is started using the current
values of the B-factors and occupancies, regardless of whether
these values are identical within a particular group.