**Definition:**

For each reflection class, the residual factor R(F^2^) calculated on the squared amplitudes of the observed and calculated structure factors for the reflections judged significantly intense (i.e. satisfying the threshold specified by _reflns_threshold_expression) and included in the refinement. The reflections also satisfy the resolution limits established by _refine_ls_class_d_res_high and _refine_ls_class_d_res_low. sum | F(obs)^2^ - F(calc)^2^ | R(Fsqd) = ------------------------------- sum F(obs)^2^ F(obs)^2^ = squares of the observed structure-factor amplitudes F(calc)^2^ = squares of the calculated structure-factor amplitudes and the sum is taken over the reflections of this class.

Appears in list containing _refine_ls_class_code

The permitted range is 0.0 -> infinity

**Type:** numb

**Category:** refine_ls_class

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