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In this article, we present the procedure of preparation of flexible electronic paper with a photosensitive azo dye layer as the key element for changing the orientation of the polarization plane. The main steps of the technology for the fabrication of flexible e-paper are reported. The possible production of Digital Mirror Devices and the roll-to-roll process is discussed. Images on flexible e-paper are demonstrated, including bank card options. The advantages of optically rewritable e-paper technology in comparison with the e-ink usually used for this purpose are highlighted. Potential applications of flexible optically rewritable e-paper include price tags for supermarkets, indoor and outdoor advertisements, smart card labels, etc.

A comprehensive theory of light-reflective characteristics and experimental technique of liquid crystal layer thickness control for flexible optically rewritable electronic paper is presented. Cylindrical pillars were used to control the gap between flexible substrates. The introduced prototype of optically rewritable electronic paper has shown very promising performance. In this regard, we report theoretical results of structural photosensitive alignment of nematic liquid crystals on flexible substrate. The focus of theoretical study is on understanding the self-assembled complex structure, governed by the interplay between surface anchoring and liquid crystal elasticity. Mueller matrix spectroscopic ellipsometry was used to study light-reflecting characteristics and polarization properties of the twisted nematic film.

The title compound [systematic name: 2-(benzyloxy)naphthalene], C17H14O, which is used as a sensitiser for thermal paper, has a twisted conformation with a dihedral angle of 48.71 (12)° between the phenyl ring and the naphthyl ring system. In the crystal, one molecule interacts with six neighbouring molecules via intermolecular C—H...π interactions to form a herringbone molecular arrangement.

In this review we describe the reversible photoalignment effect imposed on the director in nematic liquid crystals that provides an approach for fabrication of advanced optically addressed devices. Several new concepts have been developed to render photosensitive materials during the past decade. Functional soft azo dye compounds exhibiting distinct functionalities in response to polarized light are highly desirable for fabrication of optically rewritable electronic paper. An optically rewritable element base using simple and inexpensive materials can potentially enable the development of novel environmentally friendly, paper-like gadgets with improved functionality over regular electronic paper. We argue that an optically rewritable technique is relevant for some applications, where conventional paper might be irrelevant. In particular, we have tested and discussed several techniques of color and 3D image formation. This strategy for fabrication of novel devices offers versatile methods for visualization. We also show that the intensity modulation of the irradiation light has a potential to generate improved grayscale visualization. This principle is based on the statistical distribution control of photosensitive azo dye molecules, driven by the incident polarized light. Additionally, we discuss the functional characteristics of the developed prototypes.

The ability to visualize the real-time dynamics of atomic, magnetic, and electronic structure is widely recognized in many fields as a key element underpinning many important processes in chemistry, materials science, and biology. The need for an improved understanding of such processes becomes acute as energy conversion processes on fast time scales become increasingly relevant to problems in science and technology. This special issue, containing invited papers from participants at the 3rd International Conference on Ultrafast Structural Dynamics held June 10–12, 2015 in Zurich, Switzerland, discusses several recent developments in this area.

Artificial intelligence is more present than ever, both in our society in general and in science. At the center of this development has been the concept of deep learning, the use of artificial neural networks that are many layers deep and can often reproduce human‐like behavior much better than other machine‐learning techniques. The articles in this collection are some recent examples of its application for X‐ray photon science and crystallography that have been published in Journal of Applied Crystallography. [ABSTRACT FROM AUTHOR]

Crystals is instituting the Best Paper Award to recognize the outstanding papers published in the journal. We are pleased to announce the “Crystals Best Paper Award” for 2017. [...]

An annual award has been instituted to recognize the outstanding papers published in Crystals. We are pleased to announce the first “Crystals Best Paper Award” for 2015. [...]

We have selected a set of ten `golden oldies', diverse crystallography articles to illustrate important moments in the development of our field of science and which form landmark papers in crystallography. They are a mixture of `science pull and technology push'. For each of our choices, we firstly created a new title that emphasizes how the paper's importance worked out from today's perspective. Then we describe the core details and impacts of each paper, with some quotations and a selected figure or two. Ten is an arbitrary number of highlights and our choice is personal.

There are two independent molecules in the asymmetric unit of the title compound, C16H17NO4, with similar conformations but some differences in their bond angles. Each molecule adopts a trans configuration with respect to the methylidene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one molecule and 83.53 (7)° in the other. All methoxy groups are approximately coplanar with the attached benzene rings, with Cmethyl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent molecules are linked together by O—H...N and O—H...O hydrogen bonds and a π–π interaction [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H...O interactions and another π–π interaction [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.

Investigating the stories behind the makers of 3D models of crystals has proved unexpectedly unstraightforward. Drawing on actor-network theory (ANT), this article investigates the references behind a set of models of mineralogical crystals made of pasteboard held by National Museums Scotland (NMS), to uncover the history and tradition of such models and the role that pedagogy plays in their stories. The contributions of many of the main actors have been neglected, dismissed, ignored, forgotten, or otherwise rendered invisible in the historical record, either intentionally or accidentally. It became clear, however, that there was a significant tradition of modelling in paper, from the earliest years of learning, play and education. Many more people than those intending to become professional model makers were capable of making paper models of subjects from the crystals found in rocks, to buildings made of them. [ABSTRACT FROM PUBLISHER]

The use of computers and the role of women in radio astronomy and X-ray crystallography research at the Cavendish Laboratory between 1949 and 1975 have been investigated. We recorded examples of when computers were used, what they were used for and who used them from hundreds of papers published during these years. The use of the EDSAC, EDSAC 2 and TITAN computers was found to increase considerably over this time-scale and they were used for a diverse range of applications. The majority of references to computer operators and programmers referred to women, 57% for astronomy and 62% for crystallography, in contrast to a very small proportion, 4% and 13% respectively, of female authors of papers. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, C15H12O3, displays catemeric aggregation involving O—H...O hydrogen bonds progressing from the carboxyl group of one molecule to the ketone O atom of another glide-related neighbor. The molecule is twisted, with the toluene 80.61 (3)° out of plane with respect to the phenyl group of the benzoic acid. The acid group makes a dihedral angle of 13.79 (14)° with the attached phenyl ring. The molecules are achiral, but the space group glide planes create alternating conformational chirality in the chain units. The four hydrogen-bonding chains progress along [001] in an A—A—B—B pattern (right-to-left versus left-to-right), and are related to each other by the center of symmetry at (0.5, 0.5, 0.5) in the chosen cell. There is one close contact (2.54 Å) between a phenyl H atom and the acid carbonyl from a symmetry-related molecule.

The dinuclear molecule of the title compound, [Cu2(C2O4)(C18H15P)4]·2CH2Cl2, lies across an inversion center with a strictly planar bridging oxalate ligand coordinating two CuI ions via two pairs of O atoms. Two triphenylphosphine ligands also coordinate each symmetry-related CuI ion, resulting in a distorted tetrahedral geometry [O—Cu—O = 80.57 (5)° and P—Cu—P = 125.72 (2)°]. In the crystal, there are two dichloromethane solvent molecules for each dinuclear complex.

In the title molecule, C16H13N3O2S, the heterocyclic thiazine ring adopts a twist chair conformation with the S atom and an adjacent C atom displaced by 0.946 (5) and 0.405 (6) Å, respectively, on the same side of the mean plane formed by the remaining ring atoms. The mean planes of the benzene rings make dihedral angles of 16.61 (10) and 15.32 (10)° with the mean plane of the pyrazole ring. The molecular structure is consolidated by intramolecular C—H...N interactions and the crystal packing is stabilized by N—H...O and C—H...N hydrogen bonds. The crystal studied was an inversion twin with the refined ratio of the twin components being 0.53 (11):0.47 (11).

The asymmetric unit of the title compound, C36H32N22+·2I−, consists of one half-molecule of the cation and one I− anion. The cation is located on an inversion centre. The dihedral angle between the pyridinium ring and the naphthalene ring system in the asymmetric unit is 19.01 (14)°. In the crystal, the cations and the anions are linked by C—H...I interactions into a layer parallel to the bc plane. Intra- and intermolecular π–π interactions with centroid–centroid distances of 3.533 (2)–3.807 (2) Å are also observed.

Corrections are made to the name of an author in seven papers by Chinnakali et al. [Acta Cryst. (2007), E63, o4363, o4364, o4434–o4435, o4436–o4437, o4438, o4489–o4490 and o4491–o4492].

The redetermined structure of title chalcone derivative, C23H16O2, corrects errors in the title, scheme and synthesis in the previous report of the same structure [Jasinski et al. (2011). Acta Cryst. E67, o795]. There are two independent molecules in the asymmetric unit with slight differences in bond lengths and angles. The dihedral angle between the benzene ring and the anthracene ring system is 73.30 (4)° in one molecule and 73.18 (4)° in the other. Both molecules feature an intramolecular O—H...O hydrogen bond, which generates an S(6) ring. In the crystal, molecules are arranged into sheets lying parallel to the ac plane and further stacked along the b axis by π–π interactions with centroid–centroid distances in the range 3.6421 (6)–3.7607 (6) Å. The crystal structure is further stabilized by C—H...π interactions. There are also C...O [3.2159 (15) Å] short contacts.

In the title compound, C16H18NO+·C6H4ClO3S−·H2O, the cation exists in an E configuration with respect to the ethenyl bond and is slightly twisted with a dihedral angle of 9.85 (5)° between the pyridinium and the benzene rings. The anion is inclined to the cation with the dihedral angles between the benzene ring of the anion and the pyridinium and benzene rings of the cation of 78.33 (6) and 68.73 (6)°, respectively. In the crystal, the cations and anions are arranged alternately into head-to-head ribbons along the c axis, with the cationic ribbons stacked along the b axis. The crystal is consolidated by O—H...O hydrogen bonds, weak C—H...O and C—H...π interactions. π–π interactions with centroid–centroid distances of 3.6111 (7) and 3.6466 (7) Å are also observed.

In the title compound, C16H18NO+·C6H4BrO3S−·0.5CH3OH, the cation exists in the E configuration and the whole molecule of the cation, except for the O atom of the ethoxy group, is disordered with a site-occupancy ratio of 0.695 (5):0.305 (5). The cation is disordered in such a way that the ethenyl units of the major and minor components are related by 180° around the long molecular axis. In the major component, the cation is almost planar, the dihedral angle between the pyridinium and benzene rings being 0.8 (3)°, whereas in the minor component, the dihedral angle between the two aromatic rings is 4.2 (6)°. In the crystal, the cations are stacked in an antiparallel manner along the a axis, while the anions and methanol molecules are linked through O—H...O hydrogen bonds and Br...O short contacts [3.0248 (13) Å] into a tape along the same direction. The three components are further linked by weak C—H...O, C—H...Br and C—H...π interactions.

In the title compound, C17H20NO3+·I−, the cation exists in the E configuration. The pyridinium and benzene rings are close to coplanar, with a dihedral angle of 7.43 (12)° between them. The three methoxy groups of 2,4,5-trimethoxyphenyl are essentially coplanar with the benzene plane, with C—O—C—C torsion angles of 1.0 (3), −1.9 (3) and 3.6 (3)°. A weak intramolecular C—H...O interaction generates an S(6) ring motif. In the crystal, the cations are stacked in columns in an antiparallel manner along the a axis through π–π interactions, with a centroid–centroid distance of 3.7714 (16) Å. The iodide anion is situated between the columns and linked to the cation by a weak C—H...I interaction.

There are two crystallographically independent molecules in the asymmetric unit of the title compound, C18H20N2O2. The two molecules exist in an E,E configuration with respect to the two C=N double bonds. The dihedral angles between the two benzene rings in each molecule are 16.89 (6) and 18.84 (6)°. In each molecule, the two methoxy groups are coplanar with their attached benzene rings, with r.m.s. deviations of 0.0078 and 0.0336 Å in one molecule, and 0.0163 and 0.0207 Å in the other. An intramolecular C—H...O hydrogen bond is present in one molecule. In the crystal structure, molecules are arranged into ribbons along the c axis. These ribbons are further stacked along the a axis. The molecules are consolidated by C...N [3.306 (2)–3.427 (2) Å] and C...O [3.3284 (16)–3.3863 (15) Å] short contacts. C—H...π interactions are also observed.

In the title hydrated molecular salt, C16H19N2+·C6H4ClO3S−·H2O, the 2-[4-(dimethylamino)styryl]-1-methylpyridinium cation exists in an E configuration with respect to the C=C bond and is slightly twisted, with the dihedral angle between the pyridinium and benzene rings being 9.33 (10)°. In the crystal structure, the packing is stabilized by O—H...O hydrogen bonds and weak C—H...O interactions, which link the cations, anions and water molecules into chains propagating in [010]. These chains are stacked along the a axis by π–π interactions, with centroid-to-centroid distances of 3.6429 (12) and 3.6879 (12) Å; weak C—H...π interactions are also observed.

The molecule of the title chalcone, C25H20O2, consisting of 2-ethoxyphenyl and anthracene rings bridged by a prop-2-en-1-one unit, is twisted and exists in the Z configuration with respect to the central C=C bond. The dihedral angle between the benzene and anthracene rings is 78.17 (9)°. The propene unit makes dihedral angles of 44.5 (2) and 81.1 (2)° with the benzene and anthracene rings, respectively. The ethoxy substituent is almost coplanar with the attached benzene ring [C—O—C—C torsion angle = 178.57 (19)°]. In the crystal, molecules are linked into chains along the a axis by weak C—H...O interactions. The crystal structure is further stabilized by C—H...π interactions.

The cation of the title compound, C16H19N2+·C7H7O3S−·H2O, exists in the E configuration with respect to the C=C double bond and is essentially planar, the dihedral angle between the pyridinium and benzene rings being 3.55 (13)°. In the crystal, π-conjugated planes of cations and anions are inclined to each other at 84.30 (11)°. The crystal structure is stabilized by O—H...O hydrogen bonds and weak C—H...O interactions, which link the cations, anions and water molecules into chains along the b axis. These chains are stacked along the a axis by π–π interactions with centroid–centroid distances of 3.6032 (16) and 3.6462 (16) Å.

The title xanthone [systematic name: 5,13-dihydroxy-3,3,10,10-tetramethyl-3H-dipyrano[3,2-a:2′,3′-i]xanthen-14(10H)-one], C23H20O6, was isolated from the roots of Cratoxylum formosum ssp. pruniflorum. There are two molecules (A and B) in the asymmetric unit, which show chemical but not crystallographic inversion symmetry. The xanthone skeleton in both molecules is approximately planar, with an r.m.s. deviation of 0.0326 (9) Å for molecule A and 0.0355 (9) Å for molecule B from the plane through the 14 non-H atoms. The pyran rings in both molecules adopt sofa conformations. Intramolecular O—H...O hydrogen bonds generate S(5) and S(6) ring motifs. Viewed onto the bc plane, the crystal structure resembles a herringbone pattern. Stacks of molecules are stabilized by π–π interactions with centroid–centroid distances of 3.600 (5) Å. The crystal structure is further stabilized by weak C—H...O and C—H...π interactions.

The title compound, C16H16O4, a dihydrochalcone, was isolated from the rhizomes of Etlingera littoralis. The molecule is twisted with a dihedral angle of 71.69 (6)° between the two aromatic rings. The propanone unit makes dihedral angles of 4.07 (6) and 73.56 (7)°, respectively, with the 2,6-dihydroxy-4-methoxyphenyl and phenyl rings. The methoxy group is approximately coplanar with the attached benzene ring with a dihedral angle of 1.74 (10)°. An intramolecular O—H...O hydrogen bond generates an S(6) ring motif. In the crystal, intermolecular O—H...O hydrogen bonds link the molecules into chains along [201]. A π–π interaction with a centroid–centroid distance of 3.5185 (6) Å is also observed.

In the title compound, C12H22O2, the 4-methyltetrahydropyran-4-ol ring adopts a conformation close to that of a chair and with the two O atoms syn; the cyclohexyl group occupies an equatorial position and adopts a chair conformation. In the crystal packing, supramolecular chains along the b axis are sustained by O—H...O hydrogen bonds. These are connected into undulating layers in the ab plane by C—H...O interactions.

In the molecule of the title heteroaryl chalcone derivative, C21H14O2, the almost planar prop-2-en-1-one unit [r.m.s. deviation = 0.0087 (1) Å] forms dihedral angles of 5.81 (7) and 49.85 (6)°, respectively, with the furan ring and anthracene ring system. In the crystal structure, the molecules are linked into a two-dimensional network parallel to (100) by C—H...O hydrogen bonds and π...π interactions involving the furan rings [centroid–centroid distance = 3.7205 (6) Å].

The title compound [systematic name: 1,5-dihydroxy-3,6-dimethoxy-4-(2-methylbut-3-en-2-yl)-9H-xanthen-9-one], C20H20O6, is a xanthone, which was isolated from the roots of Cratoxylum formosum ssp. pruniflorum. The three rings in the molecule are approximately coplanar, with an r.m.s. deviation of 0.0372 (2) Å for the plane through the 14 non-H atoms. The O atoms of the two hydroxy substituents also lie close to this plane with deviations of 0.0669 (2) and 0.1122 (2) Å, respectively. The 1,1-dimethyl-2-propenyl substituent is in a (−)-anticlinal conformation. Intramolecular O—H...O hydrogen bonds generate S(5) and S(6) ring motifs. In the crystal, molecules are linked into infinite chains along [010] by O—H...O hydrogen bonds and weak C—H...O interactions. π–π interactions with centroid–centroid distances of 3.6172 (10) and 3.6815 (10) Å are also observed.

The complete molecule of the title compound, C10H4Cl6N2, is generated by crystallographic twofold symmetry, with two C atoms lying on the rotation axis; the 1,8-naphthyridine ring is almost planar with an r.m.s. deviation of 0.0002 Å. In the crystal structure, the molecules are stacked in an antiparallel manner along [001]. Short Cl...Cl [3.3502 (4)] and Cl...N [3.2004 (11)–3.2220 (10) Å] contacts are observed in the crystal structure.