The theory of the spin-density Patterson function

A general treatment is given of the derivation of a spin-density Patterson function from unpolarized neutron-diffraction data, showing that a peak in the function due to atoms m and n with spins Sm, Sn has a height proportional to Sm. Sn and is elongated in a direction which bisects these spin directions. The elongation is not appreciably affected even when the spin-density distributions of the atoms are highly aspherical.