Nature 246, 90 - 91 (09 November 1973); doi:10.1038/246090a0

Location of Hydrogen Atoms in ADP by Neutron Powder Profile Refinement

A. W. HEWAT^*

Materials Physics Division, UKAEA Research Group, Harwell, Berkshire
^*Now at Institut Laue-Langevin, BP156 Centre de tri, 38042 Grenoble Cedex.

NEUTRON diffraction is a powerful tool for the location of light atoms, especially hydrogen, because the neutron scattering power of these atoms is comparable to that of the heavier elements. In particular, the study of hydrogen bonding and its effect on the physical properties of molecular crystals is well suited to neutron diffraction techniques. Unfortunately, because of the relatively low flux of thermal neutrons available, even from the best reactors, rather large single crystals are required, together with expensively long periods of time for data collection. Even when large crystals can be grown, multiple scattering (extinction effects) introduce systematic errors which limit the precision with which atoms can be located. It would be important then, if some way could be found to eliminate the need for large single crystals and long periods for data collection.

References

1.	Rietveld, H. M., J. appl. Crystallog., 2, 65 (1969).
2.	Hewat, A. W., J. Phys. C., 6 (in the press).
3.	Bacon, G. E., and Pease, R. S., Proc. R. Soc., A230, 359 (1955).
4.	Tenzer, L., Frazer, B. C., and Pepinsky, Ray, Acta Crystallog., 11, 505 (1958).
5.	Nagamiya, T., Progr. theoret. Phys. Japan, 7, 275 (1952).