The xrefin optimize overall statement optimizes
overall isotropic or anisotropic B-factors
by employing a conjugate gradient minimization using
(Eq. 12.1) as the target. For the isotropic
case, the variable is simply the overall B-factor B,
and 
in Eq. 12.1 is replaced
by
For the anisotropic case, the variables are the six parameters
of the anisotropic B-factor tensor 
, and
in Eq. 12.1 is replaced
by
Normally, the following restrictions apply to the anisotropic B-factor tensor (see RESTriction statement):
After termination,
the program modifies the 
structure factors and the
B atomic property array (Section 2.16).
In the isotropic case,
it adds the refined B-factor shift to the B array and it also applies
the B-factor shift to the 
structure factors.
In the anisotropic case,
the overall isotropic contribution is subtracted from the 
tensor such that the trace of B is zero. This modified B tensor is then applied to the calculated structure factors. The overall isotropic contribution is added to the B-factor array 
.
Note that 
is not touched during this procedure.