Single crystal software

Structure Solution Using Single Crystal Software... 

While overshadowed by dedicated powder diffraction based structure solution software, single crystal structure solution programs can still be used where a list of HKLs and intensities are available and can be usefully applied (Table 17.23). This allows not only the use of Direct Methods, but also Patterson and Patterson-based fragment searching. Armel Le Bail s Overlap program (listed in Table 17.16) can remove reflections that are excessively overlapped, sometimes aiding single crystal software based structure solution. 

While computer-based structure validation is integrated in single crystal software, it is somewhat lagging in the powder diffraction community. Ton Spek s... 

We have adapted a commercially available x-ray diffractometer normally used for structure determinations on single crystals to operate as a very flexible device for performing x-ray pole figure determinations and related studies on polymeric materials. Descriptions of crystallite orientations, as provided by pole figures, are useful in studying many aspects of the behavior of products made from semicrystalline polymers. This paper describes the software that we have written for our pole figure facility. Except for some vendor-provided routines to drive the hardware Interface all of our software is written in FORTRAN. Menu driven operation is provided to maximize user convenience. 

In order to obtain detailed structure, a knowledge of diffraction intensities is essential, the intensities being related to the structure factor. Computer-controlled single-crystal X-ray diffractometers with structure (software) packages have made structure elucidation a routine matter. The availability of synchrotron X-radiation of continuously variable wavelength has made X-ray diffraction a still more powerful structural tool for the study of solids. A technique of great utility to solid state chemists is the Rietveld treatment of powder X-ray diffraction profiles (Rietveld, 1969 Manohar, 1983). Automated structure packages for the determination of unknown structures by this method are now commercially available (see section 2.2.3). In Fig. 2.1, we show a typical set of profile data. 

Crystals of 1-6 prepared as above were employed for the determination of molecular structure by single crystal X-ray diffraction. The relevant details of the crystal structures of the co-crystals are listed in Table l.f The intensity data were collected on a SMART system, Siemens, equipped with a CCD area detector,13 using Mo-Koc radiation. The structures were solved and refined using SHELXTL14 software. The refinements were uncomplicated and converged to good R-factors as... 

Qualitative and quantitative analytical applications of X-ray diffraction both require reference diffraction patterns to identify and quantify the different polymorphic modifications. Experimental powder patterns may be suspect for their use as standards as a result of experimentally induced errors or aberrations or the lack of polymorphic purity in the sample itself (which may even result from the sample preparation). The availability of full crystal structure determinations for any or all of the polymorphic modifications can considerably facilitate generation of standard powder patterns. A variety of public domain software is now available for calculating powder diffraction patterns from single crystal data (ICDD 2001, lUCr 2001)." ... 

The most comprehensive collections of various crystallographic software products are found at the International Union of Crystallography Web site at http //www.iucr.org and at the Collaborative Computational Project No. 14 for Single Crystal and Powder Diffraction Web site at http //www.ccpl4.ac.uk. 

There is a variety of software that can be used to process pseudo-single crystal experimental diffraction data represented in a form of individual structure factors or their squares (consult http //www.iucr.org and/or http //www.ccpl4.ac.uk). The most commonly used software products are SHELXS-90 and SHELXL-97 (author G.M. Sheldrick), which are distributed free for academic use (consult SHELX home page at http //shelx.uni-ac.gwdg.de/SHELX/index.html for details). Unless noted otherwise, processing of the individual structure factor data, direct phase determination, Patterson-, Fourier- and E-map calculations shown in this chapter were performed using WinCSD software, which is available from STOE Cie, Gmbh (http //www.stoe.com/products/index.htm). 

Compared to powder diffraction software, single crystal refinement programs are currently more advanced for routine structure refinement (Table 17.25). Compared to existing Rietveld software, it can be less time consuming to use a... 

Table 17.25 Available single crystal refinement and structure building software.

Hydrogen Placement Using Single Crystal and Ancillary Software... 

Free Standing Powder and Single Crystal Fourier Map Generation and Display Software... 

WinGX WinGX suite for small molecule single crystal crystallography, L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837 838 Includes and links to wide variety of validation software including Platon... 

A first port of call for checking out available crystallographic software. Links to and mirrors of single crystal and powder crystallographic software. Includes tutorials for some of the software and lists of available software Free CD ROM containing various Internet available single crystal and powder diffraction software and resources. Mainly intended for academics and students in the developing world... 

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