Once three origin-defining reflections have been assigned, the Σ₂ formula can be used to further expand the number of “known” phases. If phases can be assigned to a subset of the “strongest” reflections (usually 10 - 20% of the total number of reflections), an approximate electron density map can be calculated (this map is often called an “E-map” because it is calculated using the normalized structure factors, E_hkl, rather than the F's). Often, this first E-map will reveal the positions of all or most of the atoms in the structure.
As an example of a Direct Methods structure determination, the small organic molecule

crystallizes in the monoclinic space group P2₁/c with cell constants a = 4.997(2)Å, b = 18.191(14)Å, c = 5.112(2)Å, β = 99.42(3)°. The molecular formula is C₂HN₃O₄; a total of 1644 reflection intensities were measured of which 833 were unique.
In the table below are the 80 largest normalized structure factors in the data set (the three origin-defining reflections chosen by the computer program are labeled with asterisks):


The reader may wish to verify that these three reflections do, in fact, lead to a unique, non-redundant choice of origin!