Direct structure determination in P1 and other noncentrosymmetric symmorphic space groups

In non-centrosymmetric symmorphic space groups the correct phase set need not be the one with the best Σ₂ consistency. A new criterion (P1C - | π - (φ_{h + k}+ φ_{h - k} - 2φ_h)| is shown to be more powerful in specifying the correct phase set.