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Item _phasing_MIR_der_refln.HL_A_iso

Description

              The isomorphous Hendrickson-Lattman coefficient A~iso~ for this
               reflection for this derivative.

                         -2.0 * (Fp~obs~^2^ + Fh~calc~^2^ - Fph~obs~^2^)
                              *  Fp~obs~ * cos(alphah~calc~)
               A~iso~ =  -----------------------------------------------
                                              E^2^

               E            = (Fph~obs~ - Fp~obs~ - Fh~calc~)^2^
                              for centric reflections
                            = [(Fph~obs~ - Fp~obs~) * 2^1/2^ - Fh~calc~]^2^
                              for acentric reflections

               Fp~obs~      = the observed structure-factor amplitude of the
                              native
               Fph~obs~     = the observed structure-factor amplitude of the
                              derivative
               Fh~calc~     = the calculated structure-factor amplitude
                              from the heavy-atom model
               alphah~calc~ = the calculated phase from the heavy-atom model

               This coefficient appears in the expression for the phase
               probability of each isomorphous derivative:

               P~i~(alpha) = exp[k + A * cos(alpha) + B * sin(alpha)
                                   + C * cos(2 * alpha) + D * sin(2 * alpha)]

               Ref: Hendrickson, W. A. & Lattman, E. E. (1970). Acta
                    Cryst. B26, 136-143.

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