              Residual factor R(Fsqd) for reflections that satisfy the\
               resolution limits established by _refine.ls_d_res_high and\
               _refine.ls_d_res_low and the observation limit established by\
               _reflns.observed_criterion, calculated on the squares of the\
               observed and calculated structure factor amplitudes.\
\
                         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\
\
               sum is taken over the specified reflections