The isomorphous Hendrickson-Lattman coefficient B_iso for this reflection for this derivative. -2.0 * (Fp_obs² + Fh_calc² - Fph_obs²) * Fp_obs * sin(alphah_calc) B_iso = ----------------------------------------------- E2 ^{E = (Fph_obs - Fp_obs - Fh_calc)2} for centric reflections = [(Fph_obs - Fp_obs) * 21/2 ^{- 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 phase calculated from the heavy atom model}