X-Ray Structure Analysis

Single Crystal X-Ray Diffraction System Kappa-CCD (Bruker-Nonius)

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Single Crystal Diffractometer Kappa-CCD Goniometer with Low-Temperature Nozzle

The Nonius (now: Bruker-Nonius) Kappa-CCD diffractometer is a four-circle diffraction system, which does not consist of an Eulerian cradle but with a so-called kappa-circle. The big advantage of this setup is, that the cyrstal cooling installation does not have to follow the goniometer movemant (as it has to with the Eulerian cradle), but remains statically which guarantees a low nitrogen consumption as well as low maintenance. The reflections are detected with the help of a CCD detector, which is so sensitive, that every diffracton frame has to be taken twice to erase peaks caused by cosmic radiation. Furthermore the diffractometer is equipped with an OXFORD cryosystem 700 crystal cooling device, to temper the crystals as low as  –170°C, a crystal heater (Nonius), which is theoretically able to achieve a temperature of 1000°C for the sample crystal and a diamond anvil pressure cell. The average time to collect frames for single crystal structure solution for a mid-size crystal with lattice constants < 1200° and primitive orthorhombic symmetry is about 3 hours.

 

Single Crystal X-Ray Diffraction System IPDS-I (Stoe & Cie.)

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Single Crystal Diffractometer IPDS-I One-Circle Goniometer

The Stoe IPDS diffractometer is a one-circle diffratometer, i.e. the crystal rotates only around one axis during the measurement. The advantage of this system is that the collecting data for structure solution is not dependant on the symmetry of the crystal and thus orienting images are not necessary. The IPDS is equipped with an image plate as detector, which is coated with  BaFCl:Eu2+ (europium-doped BaFCl) that works as an X-ray phosphor. The reflections are saved on the plate and read out with the help of a laser. The average time to collect frames for single crystal structure solution is 24 hours.

 

Powder Diffraction System STADI-P (Stoe & Cie.) with Position Sensitive (PSD) and Image-Plate (IP) Detector

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Powderdiffractometer with PSD-Detector Powderdiffractometer with IP-Detector

Both the two powder diffractometers are used to investigate microcrystalline products with crystals too small for single crystal structure solution and to determine the phase purity of the products (if the by-products are crystalline as well). With the help of powder diffraction it is possible to determine and refine lattice constants and even strcutures in case of samples with a good crystallinity, however, synchrotron radiation is better suited for structure refinement from crystal powders due to its higher energy. The two STADI-P diffractometers are equipped with two camera geometries each of those using a position sensitive detector in one case one of them also using a position sensitive detector in the other case. The detector moves in an angle range from 5-120° throughout the date collection. The last camera is equipped with a bent image plate detector (detection angle 75°) which guarantees short data collection times and thus a quick glance at the phase purity of the sample but this detector is not appropriate for measurements for structure solution purposes. The samples can be mounted on a flatbed sample holder with the help of adhesive tape or in X-ray undetectable glass capilliaries und a capillary sample holder.

 

Weissenberg- and  Buerger X-ray cameras (Huber)

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Weissenberg X-ray Camera Buerger X-ray Camera

The Weissenberg- and Buerger cameras appear like relicts of former times, but they do their job very well in terms of solving crystallograohically problems like twinning. While computerized indexing programs of modern X-ray diffraktometers recognize weak reflections but do not take those into account the analyzing program of X-ray photographs is first and foremost human, which can also recognize weak reflections and draw conclusion about the "true nature" of the crystal. The X-ray used for those cameras are generated by Philips high-voltage generators. The photographical X-ray film is nowadays replaced by flexible image-plates which are read-out withthe halp of a Fujifilm BAS reader.