New software, OLEX2, has been developed for the determination, visualization and analysis of molecular crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure solution, refinement and report generation, as well as novel tools for structure analysis. OLEX2 seamlessly links all aspects of the structure solution, refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.

OLEX2: a complete structure solution, refinement and analysis program

The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and signi®cant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr Commission on Crystallographic Computing. It should not exceed 500 words in length and should follow the standard format given on page 189 of the June 1985 issue of the Journal [J. Appl. Cryst. (1985). 18, 189± 190] and on the World Wide Web at http://www.iucr. org/journals/jac/software/. Lists of software presented and/or reviewed in the Journal of Applied Crystallography are available on the World Wide Web at the above address, together with information about the availability of the software where this is known.

WinGX suite for small-molecule single-crystal crystallography

The WinGX suite provides a complete set of programs for the treatment of small-molecule single-crystal diffraction data, from data reduction and processing, structure solution, model refinement and visualization, and metric analysis of molecular geometry and crystal packing, to final report preparation in the form of a CIF. It includes several well known pieces of software and provides a repository for programs when the original authors no longer wish to, or are unable to, maintain them. It also provides menu items to execute external software, such as the SIR and SHELX suites of programs. The program ORTEP for Windows provides a graphical user interface (GUI) for the classic ORTEP program, which is the original software for the illustration of anisotropic displacement ellipsoids. The GUI code provides input capabilities for a wide variety of file formats, and extra functionality such as geometry calculations and ray-traced outputs. The programs WinGX and ORTEP for Windows have been distributed over the internet for about 15 years, and this article describes some of the more modern features of the programs.

/pdf/wingx-and-ortep-for-windows-an-update-2x46kgdygv.pdf

WinGX and ORTEP for Windows: an update

SIR97 is the integration of two programs, SIR92 and CAOS, the first devoted to the solution of crystal structures by direct methods, the second to refinement via least-squares–Fourier procedures. Several new features have been introduced in SIR97 with respect to the previous version, SIR92: greater automatization, increased efficiency of the direct methods section, and a powerful graphics interface. The program also provides publication tables and CIF files.

SIR97: a new tool for crystal structure determination and refinement

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

/pdf/prospects-of-colloidal-nanocrystals-for-electronic-and-3dxpyhl3r7.pdf

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

SIRPOW.92 – a program for automatic solution of crystal structures by direct methods optimized for powder data

SIR92 – a program for automatic solution of crystal structures by direct methods

An automatic procedure for recovering a complete crystal structure after a direct phasing process is described. The procedure consists mainly of a Fourier recycling method that can be implemented in any direct-methods package. The residual R value attained at the end of the process provides an estimate of the degree of success of the structure determination. The procedure can also be applied using a small molecular fragment as prior information. The procedure has been implemented into SIR92, the successor to SIR88.

Completion and refinement of crystal structures with SIR92

Two flexible metal-organic frameworks are presented as solid adsorbents for methane that undergo reversible phase transitions at specific methane pressures, enabling greater storage capacities of usable methane than have been achieved previously, while also providing internal heat management of the system. Natural gas — methane — is a clean and cheap fuel but its usefulness in transport applications is limited by storage problems, given its low energy density per unit volume under ambient conditions compared with petrol or diesel. One way of increasing methane storage capacity is to use tanks containing porous materials, such as metal–organic frameworks, as a storage medium. However, for every methane molecule adsorbed and desorbed there is an associated thermal fluctuation that could cause overheating or reduce storage efficiency if left unchecked. Here Jeffrey Long and colleagues describe two flexible metal–organic frameworks that undergo reversible phase transitions at specific methane pressures, enabling greater storage capacities of usable methane than have been achieved previously, while also providing internal heat management of the system. As a cleaner, cheaper, and more globally evenly distributed fuel, natural gas has considerable environmental, economic, and political advantages over petroleum as a source of energy for the transportation sector1,2. Despite these benefits, its low volumetric energy density at ambient temperature and pressure presents substantial challenges, particularly for light-duty vehicles with little space available for on-board fuel storage3. Adsorbed natural gas systems have the potential to store high densities of methane (CH4, the principal component of natural gas) within a porous material at ambient temperature and moderate pressures4. Although activated carbons, zeolites, and metal–organic frameworks have been investigated extensively for CH4 storage5,6,7,8, there are practical challenges involved in designing systems with high capacities and in managing the thermal fluctuations associated with adsorbing and desorbing gas from the adsorbent. Here, we use a reversible phase transition in a metal–organic framework to maximize the deliverable capacity of CH4 while also providing internal heat management during adsorption and desorption. In particular, the flexible compounds Fe(bdp) and Co(bdp) (bdp2− = 1,4-benzenedipyrazolate) are shown to undergo a structural phase transition in response to specific CH4 pressures, resulting in adsorption and desorption isotherms that feature a sharp ‘step’. Such behaviour enables greater storage capacities than have been achieved for classical adsorbents9, while also reducing the amount of heat released during adsorption and the impact of cooling during desorption. The pressure and energy associated with the phase transition can be tuned either chemically or by application of mechanical pressure.

Antonietta Guagliardi

Papers

SIR97: a new tool for crystal structure determination and refinement

SIRPOW.92 – a program for automatic solution of crystal structures by direct methods optimized for powder data

SIR92 – a program for automatic solution of crystal structures by direct methods

Completion and refinement of crystal structures with SIR92

Methane storage in flexible metal–organic frameworks with intrinsic thermal management