TCD-extending the limits of neutron diffraction

The focus of the Letter is to discuss ways of overcoming hitherto fundament al limitations imposed by nature on our ability to study structures by diff raction. TCD, which is based on diffraction of particles in groups correlat ed in time and space, could be the answer to some of the problems. The phys ics of TCD is discussed, which is fundamentally different to all diffractio n methods presently used. Neutrons are the most appropriate particles to "b enefit" from TCD. (C) 2001 Elsevier Science B.V. All rights reserved.