The reconstruction of large and complex unit cells from x-ray or neutron diffraction data is time consuming. If we can represent the unit cell by a set of pixels, or Ising spins, then a rapid reconstruction is possible, with use of the method of simulated annealing. This Letter discusses the requirements on the scattering density for this method to succeed in the case of very large and highly disordered unit cells. It is shown that experimental errors and contributions of delocalized electrons must be less than 1% in order to avoid a "spin-glass" ground state.

• Received 31 May 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.1966