The Chemical Database Service (CDS) is a national service, funded by the Chemistry Programme of the United Kingdom Engineering and Physical Sciences Research Council (EPSRC). It provides access for UK academics to a range of chemistry databases in the areas of crystallography, synthetic organic chemistry, spectroscopy, and physical chemistry. Three post-doctoral chemists are available to assist users with problems, run training courses, and also give advice to the community on accessing other sources of chemical data and software.

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A model and procedures are described which permit the calculation of optical and e.s.r. spectra and magnetic susceptibilities of pn, dn, or f a electron systems for any basis chosen as free-ion terms and/or states relating to a molecule of any geometry.Methods are described for calculating magnetic susceptibilities and g values in molecules whose symmetries do not predetermine the orientation of their principal molecular properties.Ligand fields are parameterized within the angular-overlap model.

Single-crystal diffraction data have been recorded for a very small crystal of dimensions 8 x 18 × 175 ~rn 3. From these data the structure of piperazine silicate (EU 19) has been determined and refined to R = 0.094 for 490 observed reflections. Data collection for such a crystal has been made practicable by the high intensity of the Daresbury Synchrotron Radiation Source and the Enraf-Nonius FAST area detector diffractometer. The potential of this synchrotron radiation method for other small crystals including proteins is discussed.

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