Neutorn powder diffraction

There is an old adage in powder diffraction that 'neutrons' are for structure refinement only, whilst X-rays are for structure determination. This chapter reviews the technique of neutron powder diffraction and shows that there are some cases where neutrons are in fact the preferred probe for structure determination. The fundamental properties of the neutron that make it such a penetrating and powerful probe are discussed and in particular, it is shown that the lack of form-factor fall-off allows diffraction data to be collected to very high (sometime sub-Ångstrom) spatial resolution, which obviously benefits structure solution. Several examples of neutron-only structure solutions are given, as are various combined X-ray/neutron solutions. The chapter concludes with an examination of possible future uses of neutron powder diffraction, considering both its strengths and weaknesses.