The use of phase combination in crystallographic refinement: the choice of amplitude coefficients in combined syntheses

When Fourier syntheses are calculated using phase information from both isomorphous replacement and the refined model it is usual to combine the information for each reflection by multiplying the two probability distributions together. It is well known that phase information from a model contains 'bias' towards that model; it is also true that such bias will be diluted by the process of phase combination. A method is proposed of tailoring the amplitude coefficients individually to correct for the likely residual bias in the combined phase.