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Overall B-Factor Refinement

    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.

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Sat Mar 11 09:37:37 PST 1995