EXAMPLES OF NON-ROUTINE APPLICATIONS FOR CCD-BASED DETECTOR SYSTEMS IN THE FIELD OF SMALL MOLECULE CRYSTALLOGRAPHY. Charles F. Campana, Siemens Energy and Automation, Inc., Analytical Instrumentation, 6300 Enterprise Lane, Madison Wisconsin 53719-1173, U.S.A., and Eric R. Hovestreydt, Siemens AG, Abt. AUT V371, Siemensallee 84, D-76181 Karlsruhe, Germany.

Over the past two years we have used standard Siemens CCD-based SMART diffractometer systems equipped with a Mo-target sealed-tube X-ray source to collected several hundred publication-quality data sets on good quality single-crystal specimens. These data sets have clearly demonstrated that this system is capable of collecting better quality data than conventional scintillation counter diffractometers in a much shorter period of time. For small or weakly diffracting crystals, measurements on the same specimen have shown that the CCD systems running at 2 kW power often yield more observed data and better structures than conventional scintillation-counter diffractometers on rotating anode generators running at 15 kW.

In addition to these studies, however, we have utilized the CCD system to investigate problems which would be very difficult, if not impossible, to pursue with conventional point-detector systems. We will present examples from our applications laboratories which demonstrate the power of CCD-based detector systems for non-routine applications. These examples will illustrate potential applications which include twinning, pseudosymmetry, superlattices, incommensurate structures, phase transitions, long axis and large unit cell problems, and characterization of non single-crystal specimens.