Phase determination for pseudo-symmetric centrosymmetric crystals

The Fourier transform of a symmetric atom group that is sampled asymmetrically by the reciprocal lattice may be deduced by inspection of the weighted reciprocal lattice. The symmetry of the atom group impresses a pseudo-symmetry on the weighted reciprocal lattice. Superposition of the pseudo-symmetric parts of the lattice gives an increased sampling of the whole Fourier transform, permits recognition of maxima and nodes, and hence provides phase information.