The systematic comparison of the atomic structure of solids and clusters has become an important task in crystallography, chemistry, physics and materials science, in particular in the context of structure prediction and structure determination of nanomaterials. In this work, an efficient and robust algorithm for the comparison of cluster structures is presented, which is based on the mapping of the point patterns of the two clusters onto each other. This algorithm has been implemented as the module CCL in the structure visualization and analysis program KPLOT.

In the past few years, new hardware tools have become available for computing using the graphical processing units (GPUs) present in modern graphics cards. These GPUs allow efficient parallel calculations with a much higher throughput than microprocessors. In this work, fast Fourier transformation calculations used in SIR2011 software algorithms have been carried out using the power of the GPU, and the speed of the calculations has been compared with that achieved using normal CPUs.

Zr–Fe-doped congruent lithium niobate single crystals were grown by the Czochralski technique. The crystal structure and lattice parameter of the grown crystals were assessed by powder X-ray diffraction and the strain developed as a result of doping has been calculated (−1.19 × 10⁻³) by using the Williamson–Hall relation. The incorporated dopant concentration along with the dopant distribution in the specimen crystal was estimated by X-ray florescence spectrometry. A multi-crystal X-ray diffraction analysis was carried out to identify the crystalline perfection of the sample and revealed that the investigated crystal does not contain any structural grain boundaries but does contain point defects and micrometre size mosaic blocks. Birefringence measurements were carried out using a prism coupler spectrometer and found that the optical birefringence is 0.0822 for 532 nm and 0.705 for 1064 nm. A thermal conductivity (κ) study reveals that the doped sample has a lower κ value than the undoped equivalent.

The influence of the gauge volume size and shape on the analysis of steep near-surface residual stress gradients by means of energy-dispersive synchrotron diffraction is studied theoretically. Cases are considered where the irradiated sample volume is confined by narrow-slit systems, in both the primary and the diffracted beam, to dimensions comparable to the `natural' 1/e information depth τ_1/e of the X-rays. It is shown that the ratio between τ_1/e, defined by the material's absorption, and the immersion depth h^GV of the gauge volume into the sample is the crucial parameter that shapes the d_ψ^hkl or ɛ_ψ^hklversus sin²ψ distributions obtained in the Ψ mode of X-ray stress analysis. Since the actual information depth 〈z〉^GV to which the measured X-ray signal has to be assigned is a superposition of geometrical and exponential weighting functions, ambiguities in the conventional plot of the Laplace stresses versus〈z〉^GV may occur for measurements performed using narrow-slit configurations. To avoid conflicts in data analysis in these cases, a modified formalism is proposed for the evaluation of the real space residual stress profiles σ_||(z), which is based on a two-dimensional least-squares fit procedure.

On the basis of the theoretical concept for the use of small gauge volumes to study near-surface residual stress fields with high spatial resolution [Meixner, Klaus & Genzel (2013). J. Appl. Cryst.46, 610–618], the experimental implementation of the approach is demonstrated. It is shown that specifically designed slit systems are required to avoid effects such as diffuse scattering at the slit blades and total external reflection, both giving rise to a reduced resolution. Starting from the characterization of the small gauge volume, practical guidance on how to control the alignment of the sample relative to the gauge volume for different geometrical conditions of energy-dispersive diffraction is given. The narrow-slit configuration as well as the formalism for data evaluation introduced in the first part of this series is applied to the analysis of a very steep in-plane residual stress gradient in a shot-peened Al₂O₃ ceramic sample. The results are compared with those obtained by means of a conventional wide-slit setup using the classical universal plot method for residual stress analysis on the one hand, and with the simulations performed in the first part on the other hand.

Residual strains measured by neutron diffraction near sample boundaries can be biased by the surface effect as a result of incomplete filling of the instrumental gauge volume. This effect is manifested as anomalous shifts of diffraction lines, which can be falsely interpreted as a lattice strain unless appropriate data corrections are made. A new analytical model for the surface effect has been developed, which covers a broad variety of instrumental arrangements, including flat mosaic and bent perfect crystal monochromators, narrow slits, and Soller and radial collimators. This model permits the spurious peak shifts to be predicted quantitatively, and also allows the optimum configuration parameters, such as curvature of a focusing monochromator, which lead to suppression of the surface effect, to be calculated. The model has been thoroughly validated by comparisons with Monte Carlo simulations and experiments on a stress-free calibration sample. Predictions of the model proved to be very accurate, often within the interval of experimental errors, which makes it suitable for use in data analysis.

The restricted volume above and below the sample on a six-circle diffractometer can limit the size and complexity of sample environments used in surface diffraction studies. An alternative configuration of the diffractometer, where the sample normal is aligned parallel to the χ axis, allows for ample space above and below the χ circle for instrumentation. The merits of this approach are outlined and angles are derived for the diffraction condition for constant-incident-angle, constant-sample-azimuthal-angle and specular geometries. Using a version of this code written for SPEC (http://www.certif.com/content/spec/), sample specular and nonspecular crystal truncation rods measured from a 5 nm-thick thin film are presented.

Polycrystalline samples of mixed Yb_1−xTb_xMnO₃ (x = 0, 0.25, 0.50, 0.75 and 1) were prepared by a solid state reaction procedure. Detailed crystal structure studies were performed using X-ray diffraction data obtained at room temperature. The application of the Rietveld method confirmed the reported hexagonal P6₃cm and orthorhombic Pnma phases for x = 0 (YbMnO₃) and x = 1 (TbMnO₃), respectively. A single hexagonal phase was also observed for x = 0.25, while in the case of x = 0.50 and x = 0.75 both phases coexist in the produced samples. Crystallographic parameters for the pure compounds are in agreement with those found in the literature. Changes in the lattice parameters, unit-cell volume, polyhedral distortions and tilting observed in the mixed compounds are explained as a function of x. Sharing of Tb³⁺ and Yb³⁺ ions between different sites is discussed.

An algorithm for determining the element-selective charge density has been developed using the maximum entropy method (MEM), Rietveld analysis and synchrotron X-ray multi-wavelength anomalous powder diffraction data. This article describes in detail both experimental and analytical aspects of the developed method. A structural study of yttrium mono-metallofullerene, Y@C₈₂, 1:1 co-crystallized with toluene using the present technique is reported in order to demonstrate the applicability of the method even when only medium resolution data are available (d > 1.32 Å). Element-selective MEM charge density maps, computed from synchrotron X-ray powder diffraction data collected at three distinct wavelengths around the yttrium K-absorption edge (∼0.727 A), are employed for determining three crystallographic sites of the disordered yttrium.

The benefits of combining experimental and computational methods have been demonstrated by a study of the dynamics and solid-state structure of α-benzophenone. Dispersion-corrected and -uncorrected density functional theory molecular dynamics simulations were used to obtain displacement parameters, with the dispersion-corrected simulations showing good agreement with the experimental neutron and X-ray diffraction values. At 70 K, quantum-nuclear effects resulted in poor values for the hydrogen atoms, but the heavy-atom values still show excellent agreement, suggesting that molecular dynamics simulations can be a useful tool for determining displacement parameters where experimental data are poor or limited.

A statistical method to determine the background level and separate signal from background in a Poisson-distributed background data set is described. The algorithm eliminates the pixel with the highest intensity value in an iterative manner until the sample variance equals the sample mean within the estimated uncertainties. The eliminated pixels then contain signal superimposed on the background, so the integrated signal can be obtained by summation or by a simple extension by profile fitting depending on the user's preferences. Two additional steps remove `outliers' and correct for the underestimated extension of the peak area, respectively. The algorithm can be easily modified to specific needs, and an application on crystal truncation rods is presented, dealing with a sloping background.

The nanoscale structural order of air-dried rat-tail tendon is investigated using small-angle X-ray scattering (SAXS). SAXS fiber diffraction patterns were collected with a superbright laboratory microsource at XMI-LAB [Altamura, Lassandro, Vittoria, De Caro, Siliqi, Ladisa & Giannini (2012). J. Appl. Cryst.45, 869–873] for increasing integration times (up to 10 h) and a novel algorithm was used to estimate and subtract background, and to deconvolve the beam-divergence effects. Once the algorithm is applied, the peak visibility improves considerably and reciprocal space information up to the 22nd diffraction order is retrieved (q = 0.21 Å⁻¹, d = 29 Å) for an 8–10 h integration time. The gain in the visibility is already significant for patterns collected for 0.5 h, at least on the more intense peaks. This demonstrates the viability of detecting structural changes on a molecular/nanoscale level in tissues with state-of-the-art laboratory sources and also the technical feasibility to adopt SAXS fiber diffraction as a future potential clinical indicator for disease.

This article presents the Monte Carlo simulation package McXtrace, intended for optimizing X-ray beam instrumentation and performing virtual X-ray experiments for data analysis. The system shares a structure and code base with the popular neutron simulation code McStas and is a good complement to the standard X-ray simulation software SHADOW. McXtrace is open source, licensed under the General Public License, and does not require the user to have access to any proprietary software for its operation. The structure of the software is described in detail, and various examples are given to showcase the versatility of the McXtrace procedure and outline a possible route to using Monte Carlo simulations in data analysis to gain new scientific insights. The studies performed span a range of X-ray experimental techniques: absorption tomography, powder diffraction, single-crystal diffraction and pump-and-probe experiments. Simulation studies are compared with experimental data and theoretical calculations. Furthermore, the simulation capabilities for computing coherent X-ray beam properties and a comparison with basic diffraction theory are presented.

A new single-crystal neutron diffractometer based on a large-area curved two-dimensional position-sensitive detector (C-2DPSD) has been developed. The diffractometer commissioning is almost complete, together with development of the measurement methodology and the raw data processing software package, the Reciprocal Analyzer, and the instrument is now ready to be launched for users. Position decoding of the C-2DPSD is via a delay-line readout method with an effective angular range of 110 × 54° in the horizontal and vertical directions, respectively, with a nominal radius of curvature of 530 mm. The diffractometer is equipped with a Ge(311) mosaic monochromator and two supermirror vacuum guide paths, one before and one after the monochromator position. The commissioning incorporates corrections and calibration of the instrument using an NaCl crystal, various applications such as crystallographic and magnetic structure measurements, a crystallinity check on large crystals, and a study on the composition or dopant content of a mixed crystal of (Tm_xYb_1−x)Mn₂O₅. The installation of the diffractometer and the measurement method, the calibration procedure and results, the raw data treatment and visualization, and several applications using the large C-2DPSD-based diffractometer are reported.

Simple processes for the preparation of semiconductor quantum dot lattices embedded in dielectric amorphous matrices play an important role in various nanotechnology applications. Of particular interest are quantum dot lattices with properties that differ significantly in different directions parallel to the material surface. Here, a simple method is demonstrated for the fabrication of an anisotropic lattice of Ge quantum dots in an amorphous Al₂O₃ matrix by a self-assembly process. A specific deposition geometry with an oblique incidence of the Ge and Al₂O₃ adparticles was used during magnetron sputtering deposition to achieve the desired anisotropy. The observed Ge quantum dot ordering is explained by a combination of directional diffusion of adparticles from the Ge and Al₂O₃ targets and a shadowing process which occurs during deposition as a result of the specific surface morphology. The prepared material shows a strong anisotropy of the electrical conductivity in different directions parallel to the sample surface.

Variant selection in friction-stir-welded high-strength low-alloy steels has been studied using the electron backscatter diffraction and prior austenite (PA) reconstruction techniques described in previous papers. A hypothesis for variant selection has been proposed based on grain-boundary interfacial energy and misorientation. This study focuses on austenite 〈111〉 boundaries with a two-dimensional approach. Results indicate that variant selection is strongly dependent on misorientation. Certain PA misorientations produce combinations of variants that minimize the interfacial energies between a ferrite nucleus and a neighboring austenite grain, and between adjoining ferrite nuclei along the boundary between two PA grains. PA grains that exhibit a 60°〈111〉 misorientation between them satisfy both these conditions for a combination of variants. These PA boundaries exhibit strong variant selection. As a result, the density of these boundary types influences the overall variant selection. Additionally, variant selection is more prevalent in small PA grains (<150 µm), which is probably a result of limited intragranular nucleation. Nearly all variants are present in larger PA grains.

A denoising method is reported for the treatment of neutron scattering data obtained with position-sensitive detectors, which enhances the information obtained from weak and very weak Bragg peaks. The core element of the method is the application of a Laplacian of Gaussian filter calculated using the parameters of the resolution of the instrument. This adaptation of well established image-processing techniques offers a very efficient way to denoise the data, as shown through the application of the reported method to a study of the magnetic Bragg peaks of a 300 nm-thick epitaxial Cr film. The procedure enhances the contrast by a factor of more than 35 and thus allows precise determination of the position of the integration mask. The large contrast enhancement also lowers the detection threshold of standard elastic neutron diffractometers down to the level usually available solely on optimized triple-axis spectrometers.

Alloys made from equimolar mixtures of more than five elements exhibit an improved thermal diffusivity at elevated temperatures, and the improvement reaches 20% at 423 K and 50% at 573 K. This phenomenon is identified from the lengthened mean free path upon thermal expansion, and lengthening scales with lattice dilation over a wide range of temperatures.

High-throughput protein crystallography projects pushed forward the development of automated crystallization platforms that are now commonly used. This created an urgent need for adapted and automated equipment for crystal analysis. However, first these crystals have to be harvested, cryo-protected and flash-cooled, operations that can fail or negatively impact on the crystal. In situ X-ray diffraction analysis has become a valid alternative to these operations, and a growing number of users apply it for crystal screening and to solve structures. Nevertheless, even this shortcut may require a significant amount of beam time. In this in situ high-throughput approach, the centering of crystals relative to the beam represents the bottleneck in the analysis process. In this article, a new method to accelerate this process, by recording accurately the local geometry coordinates for each crystal in the crystallization plate, is presented. Subsequently, the crystallization plate can be presented to the X-ray beam by an automated plate-handling device, such as a six-axis robot arm, for an automated crystal centering in the beam, in situ screening or data collection. Here the preliminary results of such a semi-automated pipeline are reported for two distinct test proteins.

Crystalline yttrium iron garnet (YIG) is an important magneto-optical material. However, this crystal is an incongruent melting compound. As is well known, compared to the crystal growth of a congruent melting compound by using the Czochralski method, the crystal growth of an incongruent melting compound is more difficult. In this work, a system for growing Ga:YIG single crystals by the edge-defined film-fed growth (EFG) method was designed and constructed, and the mechanism of crystal growth was also preliminarily studied. The Ga³⁺ dopant concentration, the Curie temperature and the transmission spectra of as-grown crystals were investigated to evaluate their potential application in magneto-optical devices. The success of growing Ga:YIG crystals by the EFG method provides a new way to grow other incongruent melting compounds.

Ru particle sizes in supported ruthenium catalysts have been studied by small-angle X-ray scattering (SAXS). It has been proposed to use new masking liquids with a relatively low X-ray radiation absorption. Using these liquids it was possible to achieve practically quantitative agreement between SAXS and transmission electron microscopy data. The SAXS technique employing such masking liquids can be used as a quick analytical method for determining the particle size distributions of supported metals. Fluorocarbon liquids can eliminate the scattering signal from any support with a density of 2.5 g cm⁻³ or less. This procedure can be very useful for selective study of separate components in complex samples consisting of carbon materials, silica materials, polymers, some hydroxides, clays etc.

The pressure-induced phase transformations of a form of amorphous silicon (a-Si) with well characterized impurity levels and structure are examined at pressures up to 40 GPa using in situ synchrotron X-ray radiation. At ∼12 GPa crystallization commences, but it is not completed until ∼16 GPa. At higher pressures, not all the crystalline phases observed for crystalline silicon (c-Si) appear. On pressure release, none of the metastable crystalline phases observed for c-Si nucleate. Instead an amorphous phase is re-formed. This is in contrast to all previous diamond-anvil studies on a-Si. If full pressure-induced crystallization occurred, the material remained crystalline on unloading. The formation of a-Si upon unloading was only observed when a high-density amorphous phase was reported on loading. The fully characterized nature of the a-Si used in this current study allows for the interpretation of this significant diversity in terms of impurity content of the a-Si used. Namely, this suggests that `ideal' (pure, voidless, structurally relaxed) a-Si will follow the same transition pathway as observed for c-Si, while crystallization of a-Si forms with a high impurity content is retarded or even inhibited. The a-Si used here straddles both regimes and thus, although full crystallization occurs, the more complex crystalline structures fail to nucleate.

This article attempts to present straightforward and easy-to-understand guidelines for the determination of element distribution in compounds lacking X-ray scattering contrast because they have similar electron counts. Different sources of anomalous dispersion correction terms (especially Δf′ values) are compared with respect to their suitability, reliability and quality. Values from databases are compared with Δf values calculated from fluorescence spectra and those refined from single-crystal diffraction data, using both reference crystals without scattering contrast problems and crystals containing elements with similar electron counts. The number of data sets required to determine reliably the element distribution and the optimum wavelengths to be used are discussed. Joint multiple data set refinements are suitable for the refinement of multiply mixed occupancies of elements lacking scattering contrast. The most straightforward method of obtaining Δf′ values depends on the complexity of the problem to be solved and the precision required.

The big bang–big crunch method is a global optimization approach developed upon the analogy of one of the cosmological theories of the evolution of the universe. It has been suitably combined with a simulated annealing algorithm and used for solving crystal structure from powder diffraction data in direct space. When compared with the traditional simulated annealing method, it provides a significant advance: good solutions are attained in a shorter time. The new method has been implemented in the EXPO package. Its successful application is demonstrated with examples of already known structures.

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010). Phys. Rev. B, 82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic `anisotropy-field' radius.

The new X-ray free-electron laser source (SwissFEL) that is currently being developed at PSI will provide a broad-bandpass mode with an energy bandwidth of about 4%. By using the full energy range, a new option for structural studies of crystalline materials may become possible. The proof of concept of broad-bandpass diffraction presented here is based on Laue single-crystal microdiffraction and the experimental setup on BL12.3.2 at the Advanced Light Source in Berkeley. Diffraction patterns for 100 randomly oriented stationary crystallites of the MFI-type zeolite ZSM-5 were simulated assuming several bandwidths, and the statistical and structural results are discussed. With a 4% energy bandwidth, the number of reflection intensities measured in a single shot is significantly higher than with monochromatic radiation. Furthermore, the problem of partial reflection measurement, which is inherent to the monochromatic mode with stationary crystals, can be overcome.

Protein crystallization conditions that resulted in crystal structures published by scientists at the MRC Laboratory of Molecular Biology (MRC-LMB, Cambridge, UK) have been analysed. It was observed that the more often a crystallization reagent had been used to formulate the initial conditions, the more often it was found in the reported conditions that yielded diffraction quality crystals. The present analysis shows that, despite the broad variety of reagents, they have the same impact overall on the yield of crystal structures. More interestingly, the correlation implies that, although the initial crystallization screen may be considered very large, it is an under-sampled combinatorial approach.

In recent years, inconsistent space groups of monoclinic B1a1 and orthorhombic B2cb have been reported for the room-temperature ferroelectric phases of both Bi₄Ti₃O₁₂ and lanthanide-substituted Bi₄Ti₃O₁₂. In this article, the electron diffraction technique is employed to unambiguously clarify the crystal symmetries of ferroelectric Bi₄Ti₃O₁₂ and Bi_3.15Nd_0.85Ti₃O₁₂ single crystals at room temperature. All the reflections observed from the two crystals match well with those derived from B1a1, but the observed reflections 010, 030, 10 and 30 should be forbidden in the case of B2cb. This fact indicates that both the ferroelectrics are of the space group B1a1 rather than B2cb, which is confirmed by convergent-beam electron diffraction observations. On the basis of the monoclinic space group B1a1, the lattice parameters of both the ferroelectrics were calculated by the Rietveld refinement of powder X-ray diffraction data.

Twiny is a small Fortran program for identification or confirmation of the twin element from the morphological analysis of twins. It takes as input the twin element and computes the angle between corresponding [uvw] directions in two individuals of the twin: the result can be used by the investigator to confirm or invalidate the supposed twin element. Twiny also accepts as input the angle measured on the sample and computes all possible twin elements compatible with this angle: the result helps the investigator to identify the twin element before any attempt to unravel the diffraction pattern of a twin.

The development of automated high-intensity macromolecular crystallography (MX) beamlines at synchrotron facilities has resulted in a remarkable increase in sample throughput. Developments in X-ray detector technology now mean that complete X-ray diffraction datasets can be collected in less than one minute. Such high-speed collection, and the volumes of data that it produces, often make it difficult for even the most experienced users to cope with the deluge. However, the careful reduction of data during experimental sessions is often necessary for the success of a particular project or as an aid in decision making for subsequent experiments. Automated data reduction pipelines provide a fast and reliable alternative to user-initiated processing at the beamline. In order to provide such a pipeline for the MX user community of the European Synchrotron Radiation Facility (ESRF), a system for the rapid automatic processing of MX diffraction data from single and multiple positions on a single or multiple crystals has been developed. Standard integration and data analysis programs have been incorporated into the ESRF data collection, storage and computing environment, with the final results stored and displayed in an intuitive manner in the ISPyB (information system for protein crystallography beamlines) database, from which they are also available for download. In some cases, experimental phase information can be automatically determined from the processed data. Here, the system is described in detail.

A Fortran90 program for the determination of the Wulff construction, starting solely from the directions of the bounding facets (defined by the user), is presented. SOWOS stands for solid of Wulff open source, and the program is distributed freely with no charge to the user, being readily available to the community for immediate use. Its simple algorithm (which will be explained) allows the determination of complex solids with hundreds of facets in just seconds on any machine, requiring only a small amount of memory. It is able to determine even the smallest facets and shortest edges and to distinguish almost adjacent vertices. The output files give a complete range of information about the structure: the coordinates of the vertices and the facets common to them, the extension of the facets and bounding vertices, and the length of the edges and extreme vertices. These details enable the reconstruction of the shape in any other (commercial) software for further processing. Visualization is straightforward via the free program gnuplot. A feature for the creation of cubic crystal atomistic models of the resultant solids is included. The program may be a useful tool for crystallography, nanostructures and any other field where crystal facets are involved.

The gradual desiccation method (GDM) is a modification of the vapor diffusion method for protein crystallization screening. This method can dramatically increase the chances of obtaining protein crystals and is therefore potentially useful for practical protein crystallization screening. However, it is troublesome to prepare the desiccant for the GDM because each of the 96 desiccants must be of the same mass. Repeated manual weighing of the desiccant (at least 96 times for one plate) to obtain the same amount is required, and manual distribution of the weighed desiccants to the respective reservoir wells is also necessary. These procedures require a considerable amount of labor and thus lower the efficiency of the screening process. Additionally, they reduce the applicability of this method in routine protein crystallization screening. To solve this problem, a high-throughput method is proposed, which involves dispensing an aqueous solution of salts (a combination of CoCl₂ and AlCl₃) into a droplet array (8 × 12, corresponding to the arrangement in a standard crystallization plate) on a piece of tape, then drying this array to obtain the final desiccant array. Simply covering and sealing this desiccant array over the crystallization droplets in the crystallization plate can give a perfect vapor diffusion screen. With this method, the labor and automation requirements of the GDM will be comparable to those of the conventional vapor diffusion method; furthermore, the amount of the desiccant can be easily and accurately controlled, allowing the GDM to be applied in daily protein crystallization screening.

GE-7031 varnish, a commonly used low-temperature adhesive and electrical insulator owing to its high thermal conductivity and mechanical strength at low temperatures, was used as a sample matrix for low-temperature powder X-ray diffraction measurements of the negative thermal expansion (NTE) material ScF₃. When ScF₃ powder was mixed with GE-7031 varnish, an unexpected cubic to rhombohedral phase transition in the ScF₃ sample was observed at ∼50 K, and it exhibited smaller low-temperature unit-cell volumes than samples without the varnish matrix. Experimental observations and quantitative estimates suggest that these anomalies are the result of stress induced by a thermal expansion mismatch between the varnish matrix (large positive coefficient of thermal expansion, CTE) and ScF₃ (quite large negative CTE). The use of GE-7031 varnish as a sample matrix for low-temperature measurements should be approached with caution if a large thermal expansion mismatch is expected.

A bespoke capillary sample holder is described that attaches to the cold head of a commercially manufactured (PheniX) closed-cycle helium cryostat originally intended for flat-plate geometry. The new holder allows high-resolution synchrotron powder diffraction data to be collected from samples in Debye–Scherrer geometry over the temperature range 11–295 K. To demonstrate that high-quality powder data can be obtained using this new sample holder, structural refinement (Rietveld) and thermal expansion results measured from reference samples (Si and Al) are presented.

The crystal structures of various important membrane proteins could not have been solved without lipidic cubic phase (LCP) crystallization, and yet, compared to traditional in surfo crystallization, LCP crystallization is not widely used because its extreme viscosity makes the cubic phase difficult to handle. Robots that can dispense LCPs are very specialized and therefore very expensive. Here, an accurate multi-channel device is described. It dispenses LCPs onto glass plates down to volumes of 20 nl accuracy and has an accuracy of 10% when dispensing 200 nl – the lower bound of LCP volumes dispensed for crystallization trials. Because of its multi-channel tips, operation speed goes up by a factor of four compared to simpler devices. It can be operated by hand, but its design also allows it to be built into a basic dispensing robot. Thus, the device lowers the threshold for LCP crystallization of membrane proteins/peptides.

A new easy-to-use device has been designed and implemented for electric field-induced protein crystallization in a vapor-diffusion configuration. The device not only controls crystal nucleation by means of the electrical current, but also favors crystal growth owing to its vapor-diffusion setup. Crystallization was conducted in the presence of an internal electric field and direct current. The proteins investigated were lysozyme, as model protein, and 2TEL–lysozyme (a synthetic protein consisting of two tandem alpha helix motifs connected to a lysozyme moiety). Lysozyme crystals that grew attached to the cathode were larger than those grown attached to the anode or in the absence of an electric current. On the other hand, crystals of 2TEL–lysozyme qualitatively showed a better X-ray diffraction pattern when grown in the presence of an electric current.