Structure solution, Patterson heavy-atom method

P(r) = P[—y)V = p u)p u + r)dv. The physical interpretation of Patterson function may be looked as the superposition of two electron densities of two unit cells whose origins are displaced origins are displaced by r [1], Sometimes, the solution of structure can be made straightforward if the structure contains a large number of light atoms and a few heavy atoms. The method is then separately named as heavy atom method and the structure factor can then be divided into two parts one due to heavy atom and the other due to light atoms and then it can be written as [1,6,7]... 

It is worth noting that practically all non-traditional methods for solving crystal structures have been initially developed for both powder and single crystal diffraction data to manage intrinsic incompleteness or poor quality that cannot be improved experimentally. Despite a variety of structure solution approaches, traditional direct phase determination methods appear to be the most common and successful when powder diffraction data are adequate. Patterson methods also work quite well but they require the presence of a heavy atom and, perhaps, more extensive crystallographic expertise. The non-traditional methods are generally employed when other techniques fail and their use is somewhat restricted by both the complexity and limited availability of computer codes. 

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