In 1934, Lindo Patterson published his keen
insight on the use of Fourier theory to narrow
the phasing search. His equation, called the
Patterson function, used diffraction intensities
to determine the interatomic distances within
a crystal, setting limits to the possible phase
values. Shortly thereafter, David Harker found
that symmetry-related atoms produced peaks
in the Patterson function at certain crystal
planes. These findings cut down on manual
computation time and allowed researchers to
examine structures of even greater
complexity, creating a boon for organometallic
crystallography, which had heavy atoms that
provided stronger diffraction intensities as
guideposts. Organic compounds as well as
molecules with more than ~50 atoms
remained a challenge.