Department of Chemistry, University of Zurich

At the Department of Chemistry, University of Zurich in Switzerland, we have been using CrysAlis^Pro since 2006. Originally, it was delivered with an Oxford Diffraction Xcalibur diffractometer. Our fleet has expanded over the years to include one of the first Oxford Diffraction SuperNova dual source diffractometers in 2010 and one of the first Rigaku Oxford Diffraction XtaLAB Synergy dual source diffractometers, with a Pilatus 200K detector, in late 2016.

We have experienced a continuous growth in the functionality, capability, flexibility and user friendliness of the software during this period. What might have started out as one of the usual diffractometer control programs, has evolved into an indispensable tool, which has the ability to obtain very good data, or better, from some of the most challenging samples. 

I can thoroughly recommend CrysAlis^Pro. General aspects of the software that I particularly like:

• The software is freely available to anyone interested, despite it being developed and maintained by a diffractometer company. This means that its use is not restricted to just the computer of the relevant diffractometer, but it may be installed on the computer of any user, thereby allowing for post-processing of data at any time without having to go back to the instrument. This is a definite advantage when the data were collected at a remote site, such as at a synchrotron. A second advantage is that there is a wider user base which tends to feed back more interesting ideas, or more readily reveals unexpected issues, to the software development team, who are open to approach and keen to correct or implement these ideas, be it with new features or helpful modifications to the GUI.
• The CrysAlis^Pro software can be downloaded from the Rigaku Oxford Diffraction forum and installed within a few seconds in a single step (additional installers are provided for StructureExplorer and AutoChem). No complex multi-step installations are required, nor are special computer administrator rights or dedicated computer accounts.
• The software development team has worked hard to adapt CrysAlis^Pro so that it can read many diffraction frame formats, not just those of their own diffractometers. This means that users of diffractometers from other companies, or of specialized detectors installed at beamlines and other locations, can take their raw data and process it with CrysAlis^Pro. Whenever new detectors appear, the software team are quite quick to update CrysAlis^Pro with the ability to read the new frame format.
• The GUI has, in my opinion, an excellent design. The procedure and workflow from initial crystal screening, through to data collection strategy development and ultimately data reduction are presented clearly. Important items and options are on the top screens and special options are on secondary screens. All of the important information is clearly visible. Sure, like any software, it takes a little getting used to initially, but users quickly come to grips with it. 
• The computation of data collection strategies utilises multiple computer cores (as does data reduction) and is thus very fast and can quickly be optimised for the desired data coverage, completeness, redundancy and so forth.
• CrysAlis^Pro offers many special options. Two examples are an excellent handling of data from twins and that one can set up automated experiments to collect data sequentially at a number of temperatures, or to collect data sequentially using both of the available X-ray wavelengths.

CrysAlis^Pro comes in two main parts. The first is the diffractometer control package, which allows the user complete flexibility to tailor the experiment exactly as desired, or, for routine work, it will guide the user deftly through the steps needed to obtain optimal data for the sample at hand. The program stores preferred strings on a user by user basis, which is handy in a multi-user environment. 

The second part is the data reduction suite (known as RED). Again, the indexing of the reflections, unit cell determination, integration of frames and application of corrections can be done fully automatically, or the user can tweak the settings for any of the sub-steps. The latter is particularly handy when treating twins, for example. Tools to visualise reciprocal space, such as Ewald Explorer, are very helpful for examining the quality of the diffraction pattern or for investigating the source of tricky problems in the data.

One caveat: while CrysAlis^Pro is very user friendly, this should never be a substitute for the novice receiving proper training and guidance from the local expert crystallographer in the lab. Nonetheless, useful online help videos or slide shows from meeting presentations are also available on the Rigaku Oxford Diffraction forum.

CrysAlis^Pro can be coupled with Rigaku Oxford Diffraction's AutoChem suite, which does require one to buy a license. This is a worth-while investment. The suite sits on the side during data collection and once every 25 frames or so attempts to solve and refine the structure using a specially optimized version of Olex² (which in turn can be linked to your favourite SHELX programs, among others). It is amazing how early on in the data collection one sees the first model for the structure displayed on the screen. At the end of the data collection, AutoChem might even produce an almost completely finished refinement model, that perhaps only requires atom relabelling and final checking. This works well for good-quality routine structures, but for more complex structures with disorder, twinning or low data quality, some further work on the model and/or the data will surely be required. In any case, it is always important to be sure that the final model has the H-atoms added correctly and that it represents the expected structure, or that it is at least consistent with, or understandable from, the chemistry when an unexpected structure arises.

An additional function in CrysAlis^Pro is active when the AutoChem module is present. Known as What is This (WIT), it allows one to do a very fast phi-scan during the initial stages of crystal screening. This can often be done within just a few minutes and AutoChem then attempts to solve the structure. Rigaku Oxford Diffraction has a cute video showing this being done on a Synergy diffractometer in less time than it takes to make a Nespresso! Some people initially thought this was a bit of a toy and gimmick, but in practice it is far from that. If the user has doubt about what compound might be in the crystal, this tool can reveal the answer within minutes and if it turns out to be something not interesting, such as a simple reagent, side-product or something previously measured, one can move on to the next sample without wasting time. If you can grow crystals, then it is almost elemental and structural analysis on the fly!

Anyone encountering difficulty with CrysAlis^Pro, or who has ideas for new features of improvements to existing ones, should not hesitate to discuss them with the software development team at Rigaku Oxford Diffraction. The input of many users over the years and the unrelenting dedication of the software development team has helped to make CrysAlis^Pro an indispensable software suite in crystallography.